Stent valve, delivery apparatus and method therefor

ABSTRACT

A delivery catheter ( 12 ) for a stent valve ( 10 ), the delivery catheter having a distal portion ( 14 ) insertable into an anatomy, the distal portion comprising an accommodation region ( 18 ) for accommodating a stent-valve for delivery into the anatomy, the delivery catheter further comprising at least one sheath ( 20; 22 ) that is translatable between a closed position for at least partly closing the accommodation region and an open position for at least partly opening the accommodation region.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a 35 U.S.C. §371 national stage entry ofPCT/EP2011/066677, which has an international filing date of Sep. 26,2011 which claims priority to U.S. patent application Ser. Nos.61/386,393, filed Sep. 24, 2010 and 61/431,710, filed Jan. 11, 2011;European Patent Application Nos. 11004013.6, filed May 15, 2011;11166201.1 filed May 16, 2011; 11006142.1 filed Jul. 26, 2011 andInternational Application No. PCT/EP2011/065744 filed Sep. 12, 2011, thedisclosures of which are incorporated herein by reference in theirentireties.

Non-limiting aspects of the present invention relate to transcatheterimplantation of prosthetic stent-valves within the anatomy, to methodsof production, and to methods and apparatus for delivering a stent-valvefor implantation at a desired implantation site. In some non-limitingaspects, the invention is directed to cardiac stent-valves and/or todelivery to the heart. Additionally or alternatively, some non-limitingaspects relate to stent-valves and their delivery via a transvascularaccess route.

Traditional approaches for aortic valve replacement require the cuttingof a relatively large opening in the patient's sternum (“sternotomy”) orthoracic cavity (“thoracotomy”) in order to allow the surgeon to accessthe patient's heart. Additionally, these approaches require arrest ofthe patient's heart and a cardiopulmonary bypass (i.e., use of aheart-lung bypass machine to oxygenate and circulate the patient'sblood). In recent years, efforts have been made to reduce invasivenessby using a transcatheter procedure, namely by delivering and implantinga prosthetic valve via a catheter inserted through a smaller skinincision, using either a transvascular route or a transapical route tothe valve implantation site. The prosthetic valve is referred to as astent-valve or a valved-stent.

While less invasive and arguably less complicated, transcatheter heartvalve replacement devices and procedures still face variousdifficulties. One issue is the unpredictability of the anatomicalcondition of the aortic valve, for example in the presence of severecalcification. Achieving controllable, consistent deployment andanchoring of a stent-valve in such variable conditions, with access onlyvia a remote catheter, is a challenge. An incorrectly positioned valvemay fail to function well, or may damage delicate heart tissue (whichmay result in the patient having to be fitted with a pacemaker), or mayresult in leakage of blood at the interface between the stent-valve andthe native tissue. A further issue for transvascular delivery isdifficulty of navigating, along a tortuous and often stenosedvasculature, a delivery catheter large enough to accommodate astent-valve for implantation. The distal end of the delivery catheter istypically in the range of 6-8 mm in diameter (18-24 French) toaccommodate the stent-valve. The design of a delivery catheter has toaddress requirements for (i) atraumatic introduction, navigation andlater withdrawal through the vasculature, and (ii) support, for example,for applying force along the length of the catheter from the proximalend, to traverse the existing valve, and manipulate the distal end tounsheath and deploy the stent-valve. These requirements often conflict,leading to compromises in design. For example, softness and flexibilityof the catheter are desired for autraumaticity and ease of navigation,but reduce the ability of the catheter to provide support for forceapplied from the proximal end remotely to the distal end. Additionalcomplications relate to the small size desired for the deliverycatheter, without affecting the reliability, accuracy or controllabilityof the deployment of the stent-valve, and ability to withdraw thecatheter following deployment of a stent, for example, through atightly-fitting introducer.

One particular type of stent-valve having a geometry promising forself-alignment and self-location even in a severely calcified nativevalve, is described in co-owned WO-A-2009/053497 and WO-A-2011/051043.The stent component comprises a conical lower anchoring crown definingan inflow end, a conical upper anchoring crown sloping outwardly in anopposite direction to the lower crown towards the outflow end, andstabilization arches at the outflow end. As described, the stabilizationarches are deployed first for aligning the stent-valve, followed bydeployment of the upper crown and finally deployment of the lower crown.A transapical delivery device is described that is easy and intuitive touse for deploying the stent-valve according to the above sequence. Itmay be desirable to refine the stent-valve and/or the delivery devicefor transvascular use.

A further issue is that it is sometimes necessary to rotate the stentabout the delivery axis, such that the stent has a certain rotationalalignment with regard to the native anatomy. Certain previouslydescribed designs of stent rely on correct rotational alignment betweenthe native anatomy and the stent, in order to locate/function correctly.Other previously shown designs of stent include apertures or clearancesthat, when aligned properly with respect to local anatomy, permit theentrance to each coronary artery to be kept relatively clear. Thisbenefits blood flow to the coronary arteries and/or permits latertreatment of the coronary arteries by allowing access for implantingcoronary stents, should this be desired for the patient in a subsequenttreatment.

In devices previously described, rotation is achieved by applying atorsional force to the catheter from the proximal handle end. Ideally,the distal end should rotate at a constant rate in response to torsionalforce. While rotation is not generally a problem with a short catheterin a relatively straight run from the handle to the stent-carrying end(e.g. transapical), it is much more problematic with a long catheterextending on a relatively twisting and/or substantially bent path (e.g.transvascular). The friction against the arterial walls obstructs freerotation, distributing the torsion to the artery itself. As thehandle-end is turned, the distal end tends to remain fixed. Thetorsional energy tends to build-up along the length of the catheteruntil the handle has been turned sufficiently that the total energyexceeds frictional resistance, whereupon the distal end springs free,and rotates through a large angle. This makes rotation adjustmentrelatively coarse, with it being extremely difficult to achieve fineadjustment. Thus, there is a need for a stent delivery system thatenables easy rotation and flexibility when delivering a stent through alonger or curving route.

The present invention has been devised bearing all of the aforementionedissues in mind. It may be desirable (although not essential) to addressand/or mitigate at least one of the foregoing issues.

Throughout this description, including the foregoing description ofrelated art, any and all publicly available documents described herein,including any and all U.S. patents, are specifically incorporated byreference herein in their entirety. The foregoing description of relatedart is not intended in any way as an admission that any of the documentsdescribed therein, including pending United States patent applications,are prior art to embodiments according to the present disclosure.Moreover, the description herein of any disadvantages associated withthe described products, methods, and/or apparatus, is not intended tolimit the disclosure. Indeed, aspects of the disclosed embodiments mayinclude certain features of the described products, methods, and/orapparatus without suffering from their described disadvantages.

Broadly speaking, one aspect of the present invention provides adelivery catheter for transvascular delivery of a stent-valve to animplantation site. The delivery catheter may be defined independently ofthe stent-valve or as part of a system in combination with astent-valve. The invention may further comprise any one or a combinationof two of more of the following features, which are all optional:

-   (a) The delivery catheter may have a distal portion for insertion    into the anatomy, and a proximal portion, a stent-valve    accommodation region at the distal portion for accommodating the    stent-valve in the compressed condition for delivery, and a stem    portion extending from the accommodation region towards the proximal    portion (e.g., to a control handle at the proximal portion). Where    defined, the stent-valve may be radially compressible to a    compressed state for delivery, and radially expandable to a    functional state. The stent-valve may comprise a plurality of valve    leaflets, and a stent component for supporting and/or housing the    valve leaflets. The stent component may be self-expanding from the    compressed state, or the stent component may be non-self-expanding    (in which case the delivery catheter may comprise a device for    applying an expansion force to cause or force expansion).-   (b) The delivery catheter may comprise may comprise a first sheath    for covering a first portion of the accommodation region and/or    stent-valve to constrain a first portion of the stent-valve    compressed, and a second sheath for covering a second portion of the    accommodation region and/or the stent-valve to constrain a second    portion of the stent-valve compressed.

The second sheath may be translatable in a proximal direction to uncoverthe second portion. The first sheath may be translatable in a distaldirection to uncover the first portion. Use of such sheaths moving inopposite directions can reduce the total distal extension of thecatheter when the sheaths are open (e.g., compared to a catheteremploying a single distally-moving sheath).

The first and second sheaths may be independently translatable.

The stem may have a smaller outer diameter than the first sheath and/orthe second sheath.

The delivery catheter may further comprise a stent holder at theaccommodation region for retaining the stent-valve in a predeterminedaxial position during deployment. The stent-holder may restrain thestent-valve against substantial axial movement (for example in both thedistal and proximal directions). The stent holder may have a profilethat mates with a portion of the stent component. For example, themating may be such as to permit self-detachment of the stent componentfrom the stent holder when the portion of the stent component matingwith the stent holder is ultimately allowed to expand by removal of arespective sheath. In some embodiments, the stent holder is positionedtowards a distal end of the accommodation region and/or is configured tomate with a distal end portion and/or inflow end portion of the stentcomponent. Optionally, the stent holder may be at least partlyoverlapped by the first sheath. Optionally, the stent holder may not beoverlapped by the second sheath.

The second sheath may be longer than the first sheath. Such anarrangement can reduce even further distal extension of the deliverycatheter when translating the sheaths to deploy the stent-valve. Theratio of the length of second sheath divided by the length of the firstsheath may, for example, be at least 1.1, or at least 1.5, or at least2, or at least 2.5, or at least 3, or at least 3.5, or at least 4, or atleast 4.5, or at least 5.

The first and second sheaths may be configured such that there is nooverlap of the ends of the sheaths with each other. Avoiding an overlapcan avoid excess diameter of the distal portion that might otherwise becaused by the sheath walls overlapping each other. The first and secondsheaths may have substantially the same internal and/or externaldiameter as each other.

In some embodiments, the first and second sheaths may, in oneconfiguration, meet substantially end to end. The delivery catheter maybe used, when containing the stent-valve ready for introduction into apatient, such that the sheaths meet substantially end to end, therebycovering the length of stent-valve substantially entirely.

Alternatively, whether or not the sheaths are capable of beingpositioned to meet end to end, in use when containing the stent-valveready for introduction into a patient, the sheath ends may be spacedapart from each other such that a portion of the stent-valve is notcovered by either sheath. The spacing between the sheaths may, forexample, be at least 1 mm, or at least 2 mm, or at least 3 mm, or atleast 4 mm, or at least 5 mm, or at least 6 mm. Additionally oralternatively, the spacing may be less than 10 mm, or less than 9 mm, orless than 8 mm, or less than 7 mm, or less than 6 mm, or less than 5 mm.In one form, the spacing is between about 4 mm and about 6 mm. Thespacing may correspond (e.g. approximately) to a region of thestent-valve in which inner and outer skirts overlap, and/or may reducestress within the stent-valve in the region of the spacing.

At the accommodation region the stent-valve may be orientated with theinflow end of the stent-valve distal of the outflow end of thestent-valve.

The catheter may further comprise an interface member, having any of theassociated features described hereinafter.

-   (c) The delivery catheter may comprise at least one sheath that is    translatable from a restraining position for restraining at least a    portion of the stent-valve compressed at the accommodation region,    to an open position in which the respective portion of the    stent-valve is uncovered for deployment from the accommodation    region; and an interface member that is deployable to provide a    guide surface for aiding withdrawal of the delivery catheter from    the anatomy after the stent-valve has been deployed. Optionally, the    catheter may be withdrawable with the interface member in a deployed    state. Optionally the interface member may be retained captive on    the delivery catheter, for example, at the accommodation region.

The interface member can provide significant performance advantages. Insome embodiments, the distal portion of the delivery catheter mayinclude one or more abrupt surfaces or edges that are exposed when theat least one sheath is translated open. The abrupt surfaces/edges may,for example, obstruct removal of the catheter through a tightly fittingintroducer if the at least one sheath remains open. Closing the at leastone sheath may be problematic if the open end an open end of the sheathinitially relies on the presence of the compressed stent-valve forconcentric relation with another part of the delivery catheter (e.g.concentricity of opposed first and second sheaths).

In some embodiments, the interface member may provide a guide surfacefor cooperating with an exposed abrupt edge of a stent holder or othercomponent of the distal portion that is exposed when the at least onesheath is open, the guide surface defining a less-abrupt and/or a morestreamlined exposed profile if the sheath remains open. The morestreamlined profile can permit the distal portion of the deliverycatheter to be withdrawn without substantial obstruction, even into andthrough a tightly fitting introducer.

Additionally or alternatively, in some embodiments, the guide surface ofthe interface member may serve to:

-   (i) at least partly cover, and/or define a profile accommodating,    the edge of the sheath at its open end, and/or-   (ii) centre the open end of the sheath with respect to an axis of    the catheter.

Such a function may permit easier closing of the sheath if desired.

In some embodiments, the delivery catheter may comprise first and secondsheaths, at least one of which is translatable as aforesaid. The othersheath may also be translatable or it may be substantially fixed. Thesheaths may have respective open ends that generally face one anotherwhen the (or each) sheath is in the closed position (whether or not thesheaths contact each other end to end).

-   In some embodiments, the interface member may be deployable to:-   (i) provide an interface at or between the generally facing open    ends, and/or-   (ii) align the open ends of the sheaths to be substantially in    register with each other and/or centred with respect to the catheter    axis, and/or (iii) define a bridge and/or a smooth profile between    the facing open ends of the sheaths.

Whatever the function of the interface member, in some embodiments, theinterface member may be translatable along the catheter axis from anon-deployed condition to a deployed condition. For example, theinterface member may initially be stowed within one of the sheaths in anon-deployed condition, and be translatable to or towards the open endof the sheath to transition to its deployed condition. In someembodiments, the interface member may be substantially freelytranslatable within a predetermined range of movement, and be configuredto move with, or in response to, sheath movement.

Additionally or alternatively, in some embodiments, the interface member(or at least a portion thereof) may be expandable. Transition from anon-deployed condition to a deployed condition may include expansion ofthe expandable portion. For example, the expandable portion of theinterface member may be radially expandable. The expandable portion maybe self-expandable from a compressed state.

In some embodiments, the interface member may be both movable andself-expandable. For example, the interface member may initially bestowed within one of the sheaths in a compressed non-deployed condition.The sheath may constrain the interface member in a compressed condition.Relative movement between the sheath and the interface member may causethe interface member to transition towards the open end of the sheath.When the interface member is no longer constrained by the sheath, theinterface member may self-expand to deploy. Upon expansion, theinterface member may float or self-position at or near the open end ofthe sheath and/or an exposed edge of the stent-holder, in its deployedcondition.

-   (d) The delivery catheter may comprise a sleeve or skirt (or    segments) of flexible material for fitting between the outer surface    of a portion of the stent-valve, and an interior surface of a    translatable sheath of the delivery catheter. The sleeve/skirt    segments may also be referred to as petals or tabs. The sleeve/skirt    (or segments) may be of flexible film or wafer material. The sheath    may translate relative to the sleeve/skirt (or segments). The    sleeve/skirt (or segments) may optionally be mounted on a stent    holder of the delivery catheter. The sleeve/skirt (or segments) may    optionally be made from balloon material of a balloon catheter, for    example, a valvuloplasty balloon catheter. Such material is strong,    resistant to tearing, yet flexible.

The sleeve/skirt (or segments) may reduce friction between the sheathand the stent-valve, for example, facilitating easier loading of thestent-valve within the sheath of the delivery catheter. The sleeve/skirt(or segments) may also avoid the sheath from catching against an edge ofan outer skirt of the stent-valve.

In some embodiments, the sleeve/skirt may comprise a sleeve sectionhaving a closed-loop shape at one end, and slits at an opposite enddefining segments that can flex outwardly independently of each other.

-   (e) In further feature similar to (d), the delivery catheter may    comprise a stent holder for mating engagement with a stent-valve    when in a compressed state for axially restraining the stent-valve    against axial movement in at least one direction, the stent holder    having attached thereto a sleeve/skirt (or segments) of flexible    material.

In some embodiments, the sleeve/skirt (or segments) may be configuredfor overlapping an outer surface portion of a stent-valve mating withthe stent holder.

In some embodiments, the stent holder may comprise a radially recessedportion for receiving a portion of a stent-valve. The sleeve/skirt (orsegments) may cover the radially recessed portion, at least in oneposition of the sleeve/skirt (or segments).

In some embodiments, the sleeve/skirt may comprise a sleeve sectionhaving a closed-loop shape at one end, and slits at an opposite enddefining segments that can flex outwardly independently of each other.

In some embodiments, the sleeve/skirt may overlap substantially theentire axial length of the stent holder.

In some embodiments, the sleeve/skirt (or segments) may be made fromballoon material of a balloon catheter, for example, a valvuloplastyballoon catheter. Such material is strong, resistant to tearing, yetflexible.

-   (f) The distal portion of the delivery catheter may comprise: at    least one sheath that is translatable from a restraining position    for restraining at least a portion of the stent-valve compressed, to    an open position in which the respective portion of the stent-valve    is uncovered for deployment; and a stent holder relative to which    the at least one sheath translates. The stent holder may be    configured to cooperate with the stent-valve for retaining the    stent-valve in a predetermined axial position during sheath    translation.

The delivery catheter may comprise a stem portion extending between thedistal and proximal ends. The stem portion may comprise a first tubewithin which a second tube is nested. One of the first and second tubesmay be coupled to the sheath, and the other to the stent holder. Thefirst and second tubes may be relatively slidable to transmit relativemotion from the proximal end to the distal end, for translating thesheath relative to the stent holder.

The second tube may be hollow to define a guide-wire lumen for receiving(directly or indirectly) a guide wire. The second tube may comprisepolyamide material and polyimide material. The polyamide and polyimidemay be layered one over the other to define an integral tubular laminatehaving a radially inner layer and a radially outer layer, for example,by coextrusion. In some embodiments, the radially inner layer may be ofpolyimide, and the radially outer layer of polyamide. However, in otherembodiments, the order could be reversed if desired. Polyimide has adesirably high modulus and strength, but is expensive to manufacture insignificant thickness. The addition of a polyamide layer can complementthe physical properties of the polyimide, providing a thicker tube ofhigh tensile and column strength, good flexibility, and high modulus.For example, the polyimide and polyamide combination can provideproperties similar to far more expensive materials such as PEEK(poly-ether-ether-ketone) tubing that is sometimes used in catheterdelivery systems.

The first tube may be of plastics in which is embedded a braid. Theplastics may, for example, be polyamide. The braid may, for example, beof stainless steel filaments.

-   (g) The stem portion may comprise tubes (referred to later as first    and third tubes) nested one within the other. The tubes may be of    plastics in which is embedded a respective braid. The braids may be    different to provide different properties. The braids may be defined    by a density or PPI (“picks per inch”) and/or by a braid angle. One    braid (for example, for the radially outer of these tubes) may have    a lower density (e.g. PPI) than the other braid (for example, for    the radially inner of these tubes). The density may, for example, be    at least twice, optionally at least 5 times, optionally at least 10    times, the density of the other. In one form, the radially inner of    these tubes may have a PPI of between 5 and 10, for example about 8.    Additionally or alternatively, the radially out of these tubes may    have a PPI of between about 50 and 100, for example, about 80.

A higher density of braid may provide good column strength by virtue ofthe amount of braid filament embedded in the tube. A good columnstrength may enable transmission of a compression force axially alongthe tube.

A lower density of braid and/or a braid angle of about 45 degrees mayprovide good for good torque transmission along the length of therespective tube. The combination of two different braid densities mayprovide better characteristics than an identical braid in both tubes.

-   (h) The stem portion may comprise at least three tubes nested one    within another, and defining at least two spaces (e.g. generally    annular but subject to relative movement between the tubes)    therebetween. The delivery catheter may further comprise a flushing    port for receiving a liquid for flushing both spaces. The same    flushing port may communicate with both the first and second spaces    to supply the liquid directly to both the first and second spaces.    Alternatively, the flushing port may communicate with one of the    first and second spaces for supplying liquid thereto, and a    communication channel may be provided for passing liquid from one    space to the other. For example, the communication channel may be an    opening in the wall of one of the tubes.

Such an arrangement can avoid having to provide a different flushingport for each space to be flushed. It can also simplify the flushingoperation for an operator.

-   (i) The delivery catheter may comprise first and second hollow    flexible tubes extending between the distal and proximal portions of    the catheter. A first tube coupling may couple the first tube to a    stent holder tube on which a stent holder is mounted. An end of the    stent holder tube may be received within the first tube at the first    tube coupling. The second tube may be nested within the first tube    and translatable relative to the first tube. The second tube may be    coupled (directly or indirectly) to a sheath for applying a    translation force to the sheath. The second tube may provide a    guide-wire receiving lumen for receiving (directly or indirectly) a    guide wire. The second tube may include a distal extension having a    smaller outer diameter than a main portion of the second tube, and    communicating therewith at an interface point. The distal extension    of the second tube may be nested within the stent holder tube, and    be translatable relative to the stent holder tube (in response to    relative translation forces being applied via the first and second    tubes). The first tube coupling may be distal of the interface point    of the second tube.

The interface point of the second tube may be spaced axially from thefirst tube coupling in the closed position of the sheath. The interfacepoint of the second tube may displace relatively towards the first tubecoupling as the sheath is moved towards its open position.

-   (j) The delivery catheter may comprise first and second flexible    tubes extending between the distal and proximal portions of the    catheter. A handle portion of the catheter may be operable to    tension and/or “pre-tension” at least one of the flexible tubes, for    example, prior to insertion into the body, and/or prior to arrival    at the desired site of implantation, and/or prior to opening of a    sheath. Pre-tensioning may avoid any tendency for the respective    tube to further elongate when a manipulation force is applied    through a neighbouring tube.

In some embodiments, the tensioned tube may be coupled to a sheath thattranslates distally from a closed position for restraining a portion ofthe stent-valve to an open position for deploying the respective portionof the stent-valve. Tensioning the tube may bias the sheath in aproximal direction, in order to restrain the sheath against distal creepwhen manipulation forces are applied through at least one other tube,for example, for translating open a second sheath.

The use of tension or “pre-tension” can avoid any need for a lockingmechanism, or sheath overlap, or additional sheath length that mightotherwise be used to counter distal creep. The use of tension cantherefore provide a more compact and/or less complicated distal portion.

-   (k) The delivery catheter may further comprise a member (e.g.    interface member) captive on the catheter, and slidable with respect    to the sheath. The member may initially be stowed within the sheath,    and may be displaced out of the sheath by relative movement of the    sheath (e.g. between the sheath and the member). The member may be    self-expandable (or include a self-expandable portion) such that,    once displaced out of the sheath, the member (or portion)    self-expands to become oversize compared to the sheath. The oversize    member may tend to remain at least partly outside the interior of    sheath.-   (l) The delivery catheter may comprise a stent holder for mating    engagement with a stent-valve when in the compressed state, for    restraining the stent-valve against axial movement, the stent holder    comprising a body having a plurality of substantially radial    projections for mating with attachment elements of a stent-valve,    each projection having at least one ramp surface extending partly    therearound to define ramp surface portions circumferentially either    side of the projection and axially to one side of the projection,    the ramp surface portions inclined outwardly away from the    projections.

With such an arrangement, the ramp surface portions may aid separationof the stent-valve attachment element from the stent-holder when thestent-valve is completed unsheathed for expansion to the functionalstate. Small axial or rotational movement of the delivery system cancause the attachment elements to ride up one of the ramp surfaceportions and be urged radially away from the stent holder, if theattachment element might otherwise remain in proximity to theprojection.

In some embodiments, the stent holder body has a portion defined bysurface of rotation in which radial recesses are provided. A respectiveprojection may project within each recess. The radial length of theprojection may be accommodated entirely or substantially within therecess. A respective ramp surface may define one axial side and oppositecircumferential sides of the recess. The other axial side of the recessmay be open. The recess may open radially outwardly.

Such an arrangement of stent holder may have a generally smooth outercontour provided by the surface of revolution. A smooth surface may, forexample, facilitate withdrawal of the distal portion of the deliverycatheter (including the stent holder) through the valve of thestent-valve following deployment of the stent-valve.

-   (m) The delivery catheter may further comprise a ball joint located    proximal of the stent accommodation region. The ball joint may be    formed in an outer tube at or leading to the distal portion.

In such a delivery catheter, the proximal portion can include a distal(first) sheath that is slidably configured to cover at least a portionof the distal end of the accommodation region and configured to slidedistally to reveal the distal end of the accommodation region for thecollapsible stent, and a proximal (second) sheath that is slidablyconfigured to cover at least a portion of the proximal end of theaccommodation region for the collapsible stent and to slide proximallyto reveal the proximal end of the accommodation region for thecollapsible stent. In some embodiments, the distal sheath and theproximal sheath meet at the proximal end of the distal sheath and thedistal end of the proximal sheath when they cover the distal andproximal ends of the collapsible stent.

The ball joint can be less than 5 cm proximal of the stent accommodationregion of the catheter. It can also be less than 2 cm proximal of thestent accommodation region of the catheter. It can also be less than 1cm of the stent accommodation region of the catheter. It can also bebetween 1 and 2 cm proximal of the stent accommodation region of thecatheter. The ball joint of the cardiac stent delivery system can alsobe hollow. Also, one or more inner tubular members can pass through thehollow portion of the ball joint. The ball joint can also allow theouter and inner tubular members to bend, according to some embodiments,at least 20° or at least 30° or at least 40° or at least 45°.

In some embodiments, the ball joint of the cardiac stent deliverycatheter can also allow an axial force to be applied on the innertubular member and the outer tubular member causing the distal sheath tobe moved distally and/or the proximal sheath to be moved proximally.This motion of the distal sheath distally and the proximal sheathproximally can reveal the collapsible stent on the attachment region,for example.

In some embodiments, the ball joint of the cardiac stent deliverycatheter can also allow the outer and inner tubular members to rotatewith regards to each other. The outer and inner tubular members can beallowed to rotate with regards to each other for one rotation, or forunlimited rotations, for example.

-   (n) The system may comprise:

an aortic stent-valve comprising a stent component and a plurality ofvalve leaflets supported by the stent component, the stent componenthaving an inflow end and an outflow end and being self-expandable from acompressed state for delivery towards a functional state uponimplantation, the stent component comprising outflow structure at ortowards the outflow end, a crown intermediate the inflow and outflowends, the crown having a free extremity intermediate the inflow andoutflow ends and directed towards the outflow end, and thestent-component further comprising a fixation section between the crownand the inflow end;

a delivery catheter having a distal portion for insertion into theanatomy, and a proximal portion, a stent-valve accommodation region atthe distal portion for accommodating the stent-valve in the compressedstate for delivery, the distal portion comprising a first sheath forcovering at least a portion of the fixation section to constrain thefixation section compressed, and a second sheath for covering at least aportion of the arches and at least a portion of the crown to constrainthe arches and the crown compressed.

The second sheath may be translatable in a proximal direction to uncoverthe crown and the outflow structure. The first sheath may betranslatable in a distal direction to uncover the fixation section. Useof such sheaths moving in opposite directions can permit at leastpartial deployment of the crown and outflow structure withoutsubstantial distal extension of the catheter. It can also reduce thetotal distal extension of the catheter when the sheaths are open(compared to a catheter employing a single distally-moving sheath).

The outflow section may comprise a plurality of arches at the outflowend each having an apex at the outflow end.

Translation of the second sheath (for example, in a proximal direction)may uncover the crown for deployment followed by uncovering the outflowstructure (e.g. arches) for deployment. Such a sequence is differentfrom that described in the aforementioned WO-A-2009/053497 andWO-A-2011/051043. Nevertheless, it has been appreciated that deployingthe outflow structure (e.g. arches) after the crown is still highlyeffective in permitting the arches to function. Notably, the outflowstructure (e.g. arches) may be deployed prior to uncovering of thefixation section for deployment.

In some embodiments, the outflow structure (e.g. arches) may beconfigured for aligning the stent-valve with respect to an axis of theascending aorta by contact with a wall of the ascending aorta. Forexample, the arches may be bendable independently of each other. Thecrown may be configured for engaging and/or seating against existingleaflets from an outflow side. The fixation section may be configuredfor engaging an existing annulus.

Deploying the outflow structure (e.g. arches) before the fixationsection may permit self-alignment of the stent-valve by the action ofthe outflow structure (e.g. arches), before the fixation section deploysto anchor the stent-valve at the annulus of the existing valve.

Further aspects of the invention relates to methods of use of thestent-valve and/or delivery catheter by using process stepscorresponding to any of those described above.

Further aspects of the invention relate to a stent-valve. Optionally,the stent-valve may be for use in a system as described above and/or foruse with a delivery catheter as described above. The followingdefinitions are therefore intended to be combined with any of theforeogoing aspects. The stent-valve may comprise a valve component and aplurality of leaflets supported by the valve component. The stent-valvemay further comprise any one or a combination of two of more of thefollowing features, which are all optional:

-   (a) The stent component may be configured to be radially    compressible into a compressed state and expandable to a functional    state. The stent component may be self-expanding from the compressed    state, or the stent component may be non-self-expanding (in which    case the delivery catheter may comprise a device for applying an    expansion force (for example, from within the stent-valve) to cause    expansion). Non-limiting example materials for a self-expanding    stent component include shape memory materials, especially metals    alloys, such as nitinol. Non-limiting example materials for a    non-self-expanding stent-component include shape memory materials,    and stainless steel.

The stent component may comprise commissural supports (e.g. posts) forsupporting the valve leaflets. The commissural supports may supportedges of valve leaflets that meet at the commissural supports.

The commissural supports may be defined by a section of the stentcomponent that is intermediate opposite end sections of the stent. Eachcommissural support may have opposite ends that each communicate with arespective stent section that is axially adjacent to the commissuralsupport. The commissural support may optionally not have a free end.

Additionally or alternatively, the commissural supports may each have aslot for receiving a tab of a leaflet. The commissural supports mayfurther comprise a plurality of bores flanking one or both long sides ofthe slot. The bores may be configured for receiving suture thread.

Additionally or alternatively, each commissural support may comprise apost. Each commissural support may have a wishbone shape. The wishboneshape may include first and second legs diverging from one end of thepost.

In some embodiments, the stent component may comprise a latticestructure having at least one row of cells, the lattice structureincluding a sequence of cells that repeats in the circumferentialdirection, the sequence including cell apexes defining: a first apexnode communicating at least with a first leg of a wishbone commissuralsupport, at least one free apex spanned by the wishbone commissuralpost, a second node apex communicating at least with a second leg of thewishbone commissural support, and at least one further node apexcommunicating with an element of a crown. The first and second nodeapexes may communicate additionally with one or more respective elementsof a crown. As mentioned above, the commissural support may comprise apost communicating at one end with the legs of the wishbone shape, andcommunicating at the other end with an outflow section of the stentcomponent (e.g. comprising stabilization arches).

The above forms of construction can provide a stent that is functionalto support a valve component, yet can be compressed to a small size.

-   (b) The stent-valve (e.g. stent component) may comprise at least one    (and preferably a plurality) of attachment elements for cooperating    with a stent-holder of the delivery catheter. Each attachment    element (or at least one of the attachment elements) may comprise a    U-shape portion joining two stent struts. The term U-shape is used    herein to include any shape including a generally arcuate apex,    whether or not the sides are straight or curved, bulged outwardly,    parallel or non-parallel. In a collapsed (e.g. compressed) condition    of the stent when received within the accommodation region of the    delivery catheter, the struts may lie adjacent each other at the    attachment element, such that the arc of the U-shape portion extends    around a first angle more than 180 degrees to define, for example, a    closed or near closed (e.g. horseshoe shape) eyelet having an    aperture larger than the spacing of the struts. The horseshoe shape    of the eyelet aperture and the adjacent space between the struts may    together define a keyhole type shape. In an expanded (or    non-collapsed) condition of the stent when released from the    accommodation region of the delivery catheter, the struts may move    apart, and the arc of the U-shape portion may extend around a second    angle that is less than the first angle, to at least partly open the    eyelet further. For example, the second angle may be about 180    degrees or less. In the expanded condition, the attached element may    define a substantially straight-sided U-shape with an arcuate apex.

The delivery catheter may comprise a sent-holder provided within theaccommodation region. The stent-holder may comprise

(i) one or more projections receivable within the eyelet. The projectionmay be dimensioned such that, when the stent is in its collapsedcondition, the projection is trapped within the eyelet and unable topass between the adjacent struts, and/or

(ii) one or more recesses or interstices for accommodating the eyeletsubstantially therewithin, at least in the collapsed state of the stent.

The above forms can provide for a compact, yet reliable and self-openingand/or self-releasing attachment between a stent-valve and a deliverysystem.

-   (c) The stent-valve may comprise at least two leaflets. The leaflets    may be of pericardium tissue, most preferably porcine pericardium    tissue or bovine pericardium. Porcine pericardium may provide    desirable tissue thinness. Bovine pericardium may be slightly    thicker but more durable.

Each valve leaflet may include at least two tabs. The tabs may serve forsupporting the leaflets relative to the stent component.

In some embodiments, the tabs may be attached directly to commissuralsupports (e.g. posts) of the stent component. The tabs may attach toattachment means provided on the commissural support. For example, a tabmay pass through a slot in a commissural support, from an interior ofthe stent component to an exterior. The portion of the tab exterior tothe stent component may be folded to lie against the commissural supportand/or sutured to the commissural support. Optionally respective tabs oftwo adjacent leaflets that meet at the commissural support pass throughthe same slot. Each tab may be folded to lie against the exterior of thecommissural support without overlapping the other tab. The two tabsoptionally are not directly attached to each other.

Additionally or alternatively, the leaflets may be attached to an innerskirt. The leaflets may be attached to an interior portion of the innerskirt, the tabs passing through slots (e.g., slits) in the inner skirtto the exterior of the inner skirt. The inner skirt may have scallopedclearances, each such clearance being spanned by a respective leaflet.The inner skirt may have commissural portions or upstands in which theslots (e.g., slits) are provided.

Additionally or alternatively, the material defining the inner skirt mayinclude integral extension portions that wrap at least around thecommissural supports, for covering the commissural supports and/or forcovering the leaflet tabs secured to the commissural supports. Theextension portions may be sutured to the commissural supports.

In some embodiments, a combination of any two or all three of the abovearrangements may be used. For example, a pair of tabs of adjacentleaflets may pass through a slot in the inner skirt, and through a slotin the commissural support. The tabs may be folded back in oppositedirections, and sutured to the exterior of the commissural support(optionally without the tabs being sutured directly to each other). Oneor more extensions of the inner skirt at the commissural support may bewrapped around the exterior of the commissural support to cover the tabsand/or the commissural support. The extension(s) may be sutured to thecommissural support. For example, the sutures may pass through the samesuture holes in the commissural support as those used for attaching thetabs. The extension(s) may extend axially beyond the tab(s), such thatthe edges of the tabs are shrouded and protected.

-   (d) The stent-valve may comprise a stent-component, a plurality of    valve leaflets mounted within the stent component, an inner skirt    attached to the valve leaflets, the inner skirt extending at least    partly within the stent component, and an outer skirt extending at    least partly outside the stent component. At least a portion of the    stent component over which at least one of the skirts extends, may    comprise a lattice structure having at least one row of a plurality    of cells.

In some embodiments, the inner and outer skirts may partly overlap, atleast with respect to the surface of at least one of the skirts.Additionally or alternatively, the inner and outer skirts may not haveany coterminous extremity. Additionally or alternatively, the outerskirt may extend further towards an inflow extremity of the stentcomponent than does the inner skirt. Additionally or alternatively, theinner skirt may extend further towards an outflow extremity of the stentcomponent than does the outer skirt.

A function of the inner skirt may be to define a conduit within thestent to channel blood towards the valve leaflets, and obstruct leakageof blood through interstices of the stent component (e.g., latticeinterstices). A function of the outer skirt may be to provide a sealsurface outside the stent component for sealing with surrounding tissue,to obstruct leakage at the interface with surrounding tissue.

Providing both skirts may be beneficial in terms of obstructing leakage.However, the presence of both skirts can add significantly to thethickness of material carried by the stent, and thereby increase thedifficulty of compressing the stent-valve to a desirably small size. Byproviding both skirts, with only partial overlap in an axial direction,the benefits of both skirts can be obtained, but with a reducedthickness profile in the regions where only one skirt extends.Overlapping the skirts can provide better sealing between the skirtsthan were the skirts to be arranged edge to edge on the interior andexterior respectively of the stent component (for example, especiallybearing in mind that the stent-valve is to be deformed substantially bycompression for delivery and re-expansion at implantation).

The degree of skirt overlap in the axial direction may, for example, byat least 1 mm, or at least 2 mm, or at least 3 mm, or at least 4 mm, orat least 5 mm, or at least 6 mm, or at least 7 mm, or at least 8 mm.Additionally or alternatively, the degree of skirt overlap in the axialdirection may, for example, be less than 10 mm, or less than 9 mm, orless than 8 mm, or less than 7 mm, or less than 6 mm, or less than 5 mm,or less than 4 mm. For example, the degree of skirt overlap in the axialdirection may be about 4-6 mm.

At least one of the skirts (optionally each skirt) may extend anon-overlapped axial distance of at least 1 mm away from the region ofoverlap. The non-overlapped distance for the or each skirt may, forexample, be at least 2 mm, or at least 3 mm, or at least 4 mm or atleast 5 mm or at least 6 mm, or at least 7 mm or at least 8 mm or atleast 9 mm, or at least 10 mm.

In some embodiments, the inflow end or edge of the stent component mayhave a zig-zag shape defined by a lattice structure of at least one rowof cells. The zig-zag shape may define an alternating sequence of freeapexes (e.g., at an inflow extremity), and connected apexes (e.g.connected to lattice structure extending away from the inflow endtowards the outflow end). In some embodiments, the inner skirt mayextend only to the connected apexes. The outer skirt may overlap theinner skirt and extend further than the inner skirt, to a levelcorresponding to at least some of the free apexes.

In some embodiments, the inner skirt may be attached to an inflow edgeand/or an outflow edge of valve leaflets. The inner skirt may extendtowards the inflow extremity of the stent component. The outer skirt mayoverlap only partly the inner skirt while remaining spaced from anuppermost edge of the inner skirt. The outer skirt may extend towards(or optionally to) the inflow extremity of the stent component. Theouter skirt may optionally not overlap (e.g., directly or indirectlythrough the stent component) any portion of the leaflets.

The inner skirt and/or outer skirt may be of any suitable material, suchas pericardial tissue (e.g. porcine pericardium for thinness), PET,Dacron, etc. The inner and outer skirts may optionally be made of thesame material as each other.

Additional aspects of the invention are defined in the claims. Althoughcertain features and ideas have been highlighted above and/or in theclaims, protection is claimed for any novel feature or idea describedherein and/or illustrated in the drawings whether or not emphasis hasbeen placed thereon.

Preferred embodiments of the invention are now described, by way ofexample only, with reference to the accompanying drawings, in which:

FIG. 1 is a schematic partial section view of a delivery catheter andstent-valve;

FIG. 2 is a schematic section showing the distal portion of the deliverycatheter partly open;

FIG. 3 is a schematic section showing the distal portion of the deliverycatheter full open;

FIG. 4 is a schematic section showing the distal portion of the deliverycatheter in more detail. The axial (horizontal) scale is compressedrelative to the radial (vertical) scale to permit all elements to beshown in a single view;

FIG. 5 is a schematic perspective view showing the distal portion of thedelivery catheter full open deploying the interface element;

FIG. 6 is a schematic side view of the interface element in isolation,shown in a deployed condition;

FIG. 7 is a schematic perspective view showing the initial closing ofthe second sheath;

FIG. 8 is a schematic perspective view showing the second sheath in itsclosed position;

FIG. 9 is a schematic side view showing the first and second sheathsreclosed with the interface element deployed;

FIGS. 10a-c are schematic sections showing in isolation exampleattachment elements of a stent-valve for attachment to a stent-holder ofthe delivery catheter. The attachment elements are shown in an expandedcondition of the stent-valve;

FIG. 11 is a schematic perspective view showing in isolation one exampleof a stent holder for the delivery catheter;

FIG. 12 is a schematic side view illustrating engagement between theattachment element of FIG. 10a and the stent holder of FIG. 11;

FIG. 13 is a schematic side view illustrating engagement between theattachment elements of FIGS. 10a /10 b and a second example of stentholder;

FIG. 14 is a schematic perspective section illustrating petals on thestent holder;

FIG. 15 is a schematic section similar to FIG. 14 illustrating acombined stent holder and interface element;

FIG. 16 is a schematic section illustrating a handle with controls atthe proximal end of the deliver catheter; and

FIG. 17 is a schematic side view illustrating one example ofstent-valve;

FIG. 18 is a schematic profile view illustrating the profile envelope ofthe stent component of the stent-valve of FIG. 17;

FIG. 19 is a schematic view illustrating a developed geometry of thestent component in a single plane;

FIG. 20 is a schematic section illustrating a liner sleeve for thecatheter;

FIG. 21 is a schematic section illustrating the interface member forstreamlining the stent holder to permit withdrawal of the catheterthrough an introducer while open. In FIG. 21, the sheaths are omitted toavoid clutter;

FIG. 22 is a schematic perspective view of a stent holder in isolation,as a single-piece item having a geometry similar to FIG. 13;

FIG. 23 is a schematic perspective view of the stent holder of FIG. 22with a sheath thereon, and mounted on the stent holder support tube; and

FIG. 24 is a schematic section illustrating a delivery catheter with aball joint.

In the drawings, the same reference numerals are used to denote thesame, or equivalent, features amongst different embodiments andexamples. Unless described to the contrary, the description of a featurein one embodiment or example may also apply to the same or equivalentfeature in another embodiment or example. Features may also beinterchanged between embodiments as desired.

Referring to FIGS. 1-3, a stent-valve 10 and a delivery catheter 12therefor are illustrated. The delivery catheter 12 may have a distalportion 14 towards one end for insertion into a patient's anatomy, and aproximal portion 16 towards an opposite end from which the deliverycatheter is manipulated in use by an operator. A barrel or stem portion15 may extend between the distal and proximal portions.

As used herein, the terms “distal” and “proximal” for the deliverycatheter may refer to relative position with respect to an operator.

The distal portion 14 of the catheter 12 may comprise an accommodationregion 18 for accommodating the stent-valve 10 in a collapsed form forintroduction into the anatomy. The stent-valve 10 may be a cardiacstent-valve. The delivery catheter 12 may be configured to permitdelivery of the stent-valve 10 to, and deployment at, a desired site ofimplantation while the heart remains beating, for example, using aminimally invasive surgical and/or percutaneous procedure. In someembodiments, the catheter 12 may be configured for introduction into theanatomical vascular system, and for advancement along the vasculaturesystem to the desired site of implantation. For example, the catheter 12may be configured for introduction into the femoral artery, and guidedretrograde via the descending aorta, aortic arch, and ascending aorta tothe heart (sometimes called a transfemoral access). The catheter 12 mayhave a length of at least about 1 m to provide sufficient lengthinsertable into the anatomy. In other embodiments, the catheter 12 maybe insertable via the subclavian artery and guided retrograde to theheart (sometimes call transubclavian access). In other embodiments, thecatheter 12 may be inserted directly into a chamber of the heart such asa ventricle (for example, left ventricle) via a direct access routewhile the heart remains beating. For example, a direct access route maybe through an aperture opened in the apex of the heart (sometimes calleda transapical access).

The size of access aperture into the anatomy may depend on the outerdiameter of the distal portion 14. The barrel portion 15 may be slightlysmaller than, or the same diameter as, the distal portion 14 as desired.For minimally invasive surgery, it is desired that the access apertureinto the anatomy be as small as practical, bearing in mind the size towhich the stent-valve 10 can be collapsed without risk of damage. Anintroducer 19, for example, a standard arterial introducer, mayoptionally be used at the access aperture into the anatomy. The optionalintroducer 19 may have a size of 20 French or smaller, for example, 18French or smaller. The distal portion 14 may be dimensioned forinsertion through such a size of introducer 19.

The stent-valve 10 may be expandable from a compressed or collapsedcondition to a functional and/or expanded condition, in order to anchorthe stent-valve 10 at the implantation site. For example, thestent-valve 10 may form a friction and/or interference fit with respectto the native anatomy. Various shapes and geometries of stent-valve 10may be used to fit the anatomy at the site of implantation. A generallycylindrical stent-valve 10 is illustrated here for clarity, but theinvention is not limited to a cylindrical shape, and may be especiallyadvantageous with non-cylindrical shaped stent-valves 10. A moredetailed example of stent-valve 10 is described later, and all detailsof the delivery catheter 12 are explicitly applicable to the stent-valveshape described later.

The stent-valve 10 may be self-expanding and/or may be configured to beexpandable by swelling of an expander (for example, a balloon notshown). Self-expanding stent-valves 10 may be constructed from, or use,shape-memory material, for example a shape-memory metal alloy (such asnitinol). A self-expanding stent-valve 10 may be retained in itscompressed state by being constrained within a sheath 20/22 of thedelivery catheter 12. Upon at least partial release from the sheath20/22, the released portion of the stent-valve 10 may be free to expand.Non-self-expanding stent-valves 10 may also be made of shape-memorymaterial, or from stainless steel, or cobalt-chromium alloy. Anon-self-expanding stent-valve 10 may also be contained at least partlywithin a sheath 20/22 to protect the stent-valve 10 and/or facilitatesmooth introduction through the anatomy.

The distal portion 14 of the catheter 12 may comprise at least onesheath 20 and/or 22 that is translatable between a closed position atleast partly covering the accommodation region 18 and/or the stent-valve10 therein, and an open position at least partly opening or exposing theaccommodation region 18 and/or at stent-valve 10 therein. In the presentexample, the catheter 12 comprises two sheaths 20 and 22, both shown intheir respective closed positions in FIG. 1 to at least partly(optionally substantially entirely) cover the stent-valve 10 in theaccommodation region 18. The sheaths 20 and 22 may be translatable inopposite directions to respective open positions. A first (e.g. moredistal) of the sheaths 20 may be translatable in a distal direction(indicated by arrow 20 a in FIG. 1) to an open position (FIG. 3). Thefirst sheath 20 may also be referred to as the distal sheath. A second(e.g. more proximal) of the sheaths 22 may be translatable in a proximaldirection (indicated by arrow 22 a in FIG. 1) to an open position (FIGS.2 and 3). The second sheath 22 may also be referred to as the proximalsheath. Use of first and second opposed sheaths 20 and 22 may providegood versatility for release of the stent-valve 12 from theaccommodation region. For example, referring to FIG. 2, by translatingthe second sheath 22 to or towards its open position without translatingthe first sheath 20, a portion 10 a of the stent-valve 10 previouslycovered by the second sheath 22 may be released (at least partly) beforea portion 10 b of the stent-valve 10 covered by the first sheath 20. Theportion 10 b may be released subsequently by translation of the firstsheath 20 to or towards its open position (FIG. 3). The length of thesecond sheath 22 may be greater than the length of the first sheath 20.For example, the ratio of the second sheath length divided by the firstsheath length may be at least 1.1, optionally at least 1.2, optionallyat least 1.3, optionally at least 1.4, optionally at least 1.5,optionally at least 1.6, optionally at least 1.7, optionally at least1.8, optionally at least 1.9, optionally at least 2.0, optionally atleast 2.1, optionally at least 2.2, optionally at least 2.3, optionallyat least 2.4, optionally at least 2.5, optionally at least 2.6,optionally at least 2.7, optionally at least 2.8, optionally at least2.9, optionally at least 3, optionally at least 3.5, optionally at least4 or optionally at least 4.5, or optionally at least 5. Use of arelatively short first sheath 20 may reduce risk of trauma in use. Thefirst sheath 20 advances distally along a path that may be lesscontrolled than the second sheath that benefits from a more controlledpath defined by the path adopted by the barrel portion 15 of thecatheter. For example, in the case of transvascular access (e.g.transfemoral access), the first sheath 20 may advance into the ventricleof the heart. Use of a relatively short first sheath 20 may reduce thedegree to which the catheter 12 has to penetrate into the ventricle, andrisk interfering with delicate tissue surfaces. In the case of directaccess (e.g. transapical access), the first sheath 20 may advance intothe ascending aorta. Use of a relatively short first sheath 20 mayreduce the degree to which the first sheath 20 has to penetrate thespace of the ascending aorta, and risk interfering with the aorta wall.

One or both of the sheaths 20 and 22 may be of plastics optionallyincluding reinforcement to resist radial expansion of the sheath. Onesuitable plastics is a poly ether block amide (PEBA), for example PEBAX(TM). Reinforcement may be provided by a helical coil embedded withinthe sheath. The helical coil may be of metal, for example, stainlesssteel filament.

The sheaths 20 and 22 may have the same inner and/or outer diameter. Thesheaths 20 and 22 may be configured not to overlap each other. Avoidingan overlap can avoid excess diameter of the distal portion that mightotherwise be caused by the sheath walls overlapping each other.

The sheaths 20 and 22 may be capable of being positioned such that thesheaths 20 and 22 meet substantially end to end. Alternatively, thesheaths 20 and 22 may be configured such that the sheaths 20 and 22always remain spaced from each other, even in mutually closed positionsof the first and second sheaths 20 and 22. For example, the minimumspacing may be at least 1 mm, or at least 2 mm, or at least 3 mm, or atleast 4 mm, or at least 5 mm, or at least 6 mm. Additionally oralternatively, the spacing may be less than 10 mm, or less than 9 mm, orless than 8 mm, or less than 7 mm, or less than 6 mm, or less than 5 mm.In one form, the spacing is between about 4 mm and about 6 mm.

During the translations of the sheaths 20 and 22 a stent-holder 24 mayretain the stent-valve 10 axially in position and/or restrain thestent-valve 10 against axial movement. The stent-holder 24 isrepresented purely schematically in FIGS. 1-3, and is described in moredetail later. The stent-holder 24 may prevent and/or obstruct anytendency of the stent-valve 10 to be dragged by translation of a sheath20 or 22. Additionally or alternatively, the stent-holder 24 may preventand/or obstruct any tendency for a self-expanding stent-valve 10 to jumpfree of the catheter if only a small portion of the stent-valve 10remains constrained by the sheath 20 or 22. The stent holder 24 may bepositioned in the accommodation region 18 at a position appropriate toengage the stent-valve 10 until final release of the stent-valve 10 fromthe accommodation region. In the illustrated example, a distal portionof the stent-valve 10 may be intended to be released last, and thestent-holder 24 may be positioned towards the distal end of theaccommodation region 18. In other embodiments, if the proximal portionof the stent-valve 10 is intended to be released last, the stent-holder24 could instead be positioned towards the proximal end of theaccommodation region 18.

FIG. 4 illustrates one example construction of the distal portion 14 ofthe catheter 12 in more detail. The barrel portion 15 comprises aplurality of flexible tubes 26, 28 and 30 extending between the distalportion 14 and the proximal portion 16. The tubes 26-30 may be nested atleast one within another, and coupled to the sheaths 20 and 22 and thestent holder 24. The sheaths 20 and 22 may be translated by relativetranslation of respective tubes. At least one, optionally two,optionally three, optionally more, of the flexible tubes may be ofplastics, optionally with reinforcement.

For example, at least one tube may comprise a combination of polyamidematerial and polyimide material. The polyamide and polyimide may belayered one over the other to define an integral tubular laminate havinga radially inner layer and a radially outer layer, for example, bycoextrusion. In some embodiments, the radially inner layer may be ofpolyimide, and the radially outer layer of polyamide. However, in otherembodiments, the order could be reversed if desired. Polyimide has adesirably high modulus and strength, but is expensive to manufacture insignificant thickness. The addition of a polyamide layer can complementthe physical properties of the polyimide, providing a thicker tube ofhigh tensile and column strength, good flexibility, and high modulus.For example, the polyimide and polyamide combination can provideproperties similar to far more expensive materials such as PEEK(poly-ether-ether-ketone) tubing that is sometimes used in catheterdelivery systems.

Additionally or alternatively, reinforcement may be provided by a braid,for example, a metal braid, within the plastics. The plastics may, forexample, be a polyamide, and/or the braid of stainless steel filament.The reinforcement may, compared to a tube of the same plastics withoutthe reinforcement: (i) increase the modulus of elasticity yet retainflexibility; and/or (ii) improve resistance to kinking when the tube isflexed; and/or (iii) increase the ability for transmission of torquefrom the proximal portion to the distal portion. Respective differenttubes may have respective different braids. The braids may be defined bya density or PPI (“peaks per inch”) and/or by a braid angle. Forexample, a lower density may imply that the winding angle is closer tothe axial direction; a higher density implies that the winding angle iscloser to the radial direction. One braid (for example, a more radiallyouter tube) may have a lower density (e.g. PPI) than another braid (forexample, for a more radially inner tube). The density may, for example,be at least twice, optionally at least 5 times, optionally at least 10times, the density of the other. A higher density may provide forgreater column strength. A lower density and/or a braid angle closer to45 degrees may provide for greater torque transmission. The combinationof two different braid densities may provide better characteristics thanan identical braid in both tubes. In some embodiments, one tube may havea braid PPI of between about 5 and about 10, for example, about 8.Additionally or alternatively, the other tube may have a braid PPI ofbetween about 50 and about 100, for example, about 80.

Referring to the specific structure in FIG. 4, a first tube 26 may becoupled for controlling the stent holder 24. The first tube 26 mayoptionally comprise plastics with braid reinforcement, as describedabove. A first tube coupling 34 may couple the first tube 26 to a stentholder support tube 32 on which the stent holder 24 is mounted. Forexample, the stent holder support tube 32 may be inserted into the endof the first tube 26 and/or attached thereto, at the first tube coupling34. The stent holder support tube 32 may have a smaller outer diameterthan the first tube 26. The stent holder support tube 32 may be lessflexible than the first tube 26. The stent holder support tube 32 may,for example, be of polyimide. The stent holder support tube 32 may actas an extension of the first tube 26 adapted to pass within therelatively confined space of the accommodation region 18. The reducedflexibility can compensate for smaller diameter to provide adequatecolumn strength along the axis of the stent holder support tube 32.

A second tube 28 may be coupled to control the first (distal) sheath 20.The second tube 28 may optionally comprise a tubular laminate of apolyimide layer radially within a polyamide layer, including any of theassociated details described above. The second tube 28 may be nestedwithin the first tube 26 and be translatable relative thereto. Thesecond tube 28 may include a distal extension 38 having a smaller outerdiameter than a main portion of the second tube, and communicatingtherewith at an inter-face point 36. The distal extension 38 may, forexample, be an extension of the polyimide inner layer without thepolyamide outer. The distal extension 38 may support (directly orindirectly) the first sheath 20. The sheath 20 is mounted to the distalextension 38 by a tip member 40. The tip member 40 may have a taperedatraumatic shape to aid advancement of the catheter 12 within theanatomy without trauma to the surrounding anatomy. The tip member 40 mayhave a rear extension 42 around which the first sheath 20 is attachedimmovably to the tip member 40. The smaller outer diameter of the distalextension 38 may be configured to pass within the small diameter of thestent holder support tube 32. The distal extension 38 may translatewithin the stent holder support tube 32, and move therewithin as thesecond tube 28 moves within the first tube 26. To move the first sheath20 to its open position, a translation force may be applied to advancethe second tube 28 distally relative to the first tube 26. Thetranslation force and movement is applied from the second tube 28 to thedistal extension 38, which pulls the first sheath 20 distally (forexample, the translation force and movement being applied through thetip member 40). Concurrently, the stent holder 24 may hold thestent-valve 10 relatively stationary under the control of the first tube26 and the stent holder support tube 32 on which the stent holder 24 ismounted.

The optional diameter difference between the first tube 26 and the stentholder support tube 32 may define a profile step or change at the firsttube coupling 34. The optional diameter difference between the secondtube 28 and the distal extension 38 may define a profile step or changeat the interface point 36. The outer diameter of the second tube 28 maybe greater than the inner diameter of the stent holder support tube 34(for example such that the second tube cannot translate beyond the firsttube coupling 34). In the closed position of the first sheath 20, thefirst tube coupling 34 and the interface point 36 may be spaced apart.The interface point 36 may be proximal of the first tube coupling 34.The spacing may be at least as large as the amount of linear translationof the first sheath 20 when the sheath moves between its open and closedpositions. The spacing may permit the interface point 36 to advancedistally.

The second tube 28 and the distal extension 38 may define a lumen 46extending through the catheter. The lumen 46 may be a guidewirereceiving lumen for receiving a guide wire (not shown) along which thecatheter 12 may be advanced within the anatomy to guide the distalportion 14 to the desired site of implantation.

A third tube 30 may be coupled for controlling the second (proximal)sheath 22. The third tube 30 may optionally comprise plastics with braidreinforcement, as described above. The first tube 26 may be nested withthe third tube 30. The third tube may be translatable relative to thefirst tube 26 and/or the second tube 28. A third tube coupling 44 maycouple the third tube 30 to the second sheath 22. The third tubecoupling 44 may include a tapered surface for defining a smoothatraumatic transition between the outer surfaces of the third tube 30and the second sheath 22. The third tube coupling 44 may be integralwith the second sheath 22, and may be a narrowed end portion thereof.

To move the second sheath 32 to its open position, a translation force(e.g. tension) may be applied to retract the third tube 30 proximallyrelative to the first tube 26. The translation force and movement isapplied from the third tube 30 to the second sheath 22, which pulls thesecond sheath 22 proximally. Concurrently, the stent holder 24 may holdthe stent-valve 10 relatively stationary under the control of the firsttube 26 and the stent holder support tube 32 on which the stent holder24 is mounted.

As described above, the braids in the first and third tubes 26 and 30may have different characteristics according to their respective innerand outer radial relationship.

The sequential order in which the first and second sheaths aretranslated to their open position may depend on the design of thestent-valve. In at least some embodiments, the second sheath 22 may betranslated before the first sheath 20. An example deployment sequence isdescribed later.

Also, in some embodiments, at least one of the tubes may bepre-tensionable at least prior to opening the distal potion 14 fordeploying a stent-valve. Pre-tensioning the tube may compensate for anytendency of the portion of the catheter controlled by the tube to creepdistally in response to forces applied during manipulation to open otherportion(s) of the catheter controlled by other tube(s). For example, thesecond tube 28 may be pre-tensioned from the proximal end, in order toprevent the first sheath 20 from creeping distally when the secondsheath 22 is pulled back while applying a maintaining force to the firsttube 26. Creeping of the first sheath 20 is undesirable as it may resultin movement of the deployment position, or premature release of thestent. Pre-tensioning the second tube 28 may maintain the first sheath20 firmly closed, thereby preventing premature release. When it isdesired to open the first sheath 20 by applying a pushing force throughthe second tube 28, the pre-tension is removed as part of the transitionto applying a pushing force. The pre-tension may be generated bycontrols within the handle, as described later. The amount ofpre-tension may be sufficient to counter the reaction force appliedthrough the first tube when translating the third tube to move thesecond sheath proximally. The amount of pre-tension appropriate for aspecific embodiment of delivery catheter may, for example, be derivableempirically.

The above arrangements can provide a delivery catheter that combines thedesirable properties of compact size, good flexibility without kinking,good transmission of torque, good column strength, and avoidance ofdistal creep of a sheath, all without using exotic materials that areprohibitively expensive.

Where additional flexibility is desired, the invention also contemplatesinclusion of a ball joint (not shown) that is just proximal of thedistal portion. The ball joint may be provided in the third tube, or theconnecting portion between the third tube and the second sheath. Theball joint may be hollow to allow the first and second tubes to passtherethrough.

As may be seen generally in FIGS. 1-4, the first and second sheaths 20and 22 may have respective mouths or open ends 20 b, 22 b, respectively,that may generally confront or lap one another when the (or each) sheath20, 22 is in the closed position, or may remain slightly spaced apart.In the illustrated embodiments, both sheaths 20 and 22 are translatable,but in some embodiments it is possible that only one of the sheaths 20and 22 might be translatable.

Prior to release of the stent-valve 10, the presence of the stent-valve10 within the accommodation region 18 may cause the sheaths 20 and 22 tobe generally aligned in register. Even if the open ends 20 b and 22 bare spaced from each other or confront each other without lapping, theopen ends 20 b and 22 b may thus align in register. Such alignment mayavoid any abrupt edges in the outer profile of the sheaths, andfacilitate insertion of the distal portion 14 into the anatomy(optionally through the introducer 19 and/or advancement throughvasculature). However, after the stent-valve 10 has been released fromthe accommodation region 18, if the operator may desire to close thesheaths, there may be a tendency for the open ends 20 b and 22 b nolonger to be closely aligned. Such misalignment may result in an abruptedge in a case of confronting or slightly spaced open ends and/ordifficulty of re-engaging the open ends in the case of trying to lap theopen ends. It may be desirable to avoid an abrupt edge, especially atthe open end 20 b of the first sheath 20. When the catheter 12 iswithdrawn after having released the stent-valve 10, the open end 20 bmay interfere with native tissue on the return path, or it may make itdifficult to extract the distal portion through an introducer 19,especially if the distal portion 14 is a tight fit within the introducer19. During such withdrawal, the second sheath 22 may be guided smoothlyinto the introducer 19 by the ramp surface 44 at the third tube coupling44. However, an abrupt edge at the open end 20 b of the first sheath 20may obstruct smooth passage of the first sheath 20 for withdrawalthrough the introducer 19.

Alternatively, if the catheter 12 is withdrawn with one or both of thesheaths 20 and 22 in an open condition, an exposed abrupt edge (e.g. endface 92 in FIGS. 11-13) of the stent holder 24 may make it difficult toextract the distal portion through an introducer 19, especially if thedistal portion 14 is a tight fit within the introducer 19. During suchwithdrawal, the second sheath 22 may be guided smoothly into theintroducer 19 by the ramp surface 44 at the third tube coupling 44.However, the abrupt edge 92 of the stent holder 24 may obstruct smoothpassage of the first sheath 20 for withdrawal through the introducer 19.

To address this, the distal portion 14 may comprise an interface member50 (FIGS. 4 to 9). The interface member 50 may be deployable to:

-   (i) provide an interface at or between the generally confronting    open ends 20 b and 22 b when (at least nearly) closed; and/or-   (ii) align the open ends 20 b and 22 b to be substantially in    register with each other and/or centred with respect to the catheter    axis; and/or-   (iii) define a bridge and/or a smooth profile between the    confronting open ends 20 b and 22 b; and/or-   (iv) provide an interface for the stent-holder 24 less abrupt than    the exposed edge 92.

In some embodiments, the interface member 50 may be deployable as partof the sequence during or after release of the stent-valve 10.

In some embodiments, the interface member 50 may be translatable alongthe catheter axis from a non-deployed condition (FIG. 4) to a deployedcondition (FIGS. 5 to 9). For example, the interface member 50 may beinitially be stowed within one of the sheaths (for example the secondsheath 22) in a non-deployed condition, and be translatable to ortowards the open end of the sheath (22) to transition to its deployedcondition. Stowing a movable interface member 50 initially within thesecond sheath 22 may avoid having to elongate the first sheath 20unnecessarily to accommodate the interface member 50. As illustratedbelow, in some embodiments, the interface member 50 may be substantiallyfreely translatable within a predetermined range of movement, and beconfigured to move with, or in response to, sheath movement. Theinterface member 50 may be referred to as a shuttle. The interfacemember 50 may be slidable (e.g. captively slidable) on one of the tubes26, 28, 32, 38.

In some embodiments, the interface member 50 (or at least a portion 52thereof) may be expandable. Transition from a non-deployed condition(FIG. 4) to a deployed condition (FIGS. 5 to 9) may include expansion ofthe expandable portion 52. For example, the expandable portion 52 of theinterface member may be radially expandable. The expandable portion maybe self-expandable from a compressed state.

In the illustrated embodiment, the interface member 50 may be bothmovable and self-expandable. Referring to FIG. 4, the interface member50 may initially be stowed within one of the sheaths (for example thesecond sheath 22 as mentioned above) in a compressed non-deployedcondition. The sheath 22 may constrain the interface member 50 in acompressed condition. The interface member 50 may be accommodated at oneend of the accommodation region 18 where the interface member 50 may notinterfere with the stent-valve 10.

As part of the release of the stent-valve 10 as explained above, thesecond sheath 22 may be retracted proximally. However, travel of theinterface member 50 in the proximal direction may be restrained, forexample, by the step profile of the first tube coupling 34. Retractionof the second sheath 22 may therefore cause relative movement betweenthe second sheath 22 and the interface member 50, resulting in theinterface member 50 transitioning towards the open end 22 b of thesheath 22. When the interface member 50 may no longer be constrained bythe sheath 22, the interface member 50 (or the portion 52) mayself-expand. Upon expansion, the interface member 50 may become toolarge to be received again entirely within the sheath 22. The interfacemember 50 may at least partly “float” captive on the catheter betweenthe stent holder 24 and the second sheath 22.

In some embodiments, it be may desired to re-close the sheaths 22 and 24prior to removing the catheter 12 from the body. When the second sheath22 is reclosed after release of the stent-valve 10, the interface member50 may at least partly self-locate or “float” at the open end 22 b. Theinterface member 50 may be pushed distally towards the stent holder 24and/or the open end 20 b of the first sheath. Optionally, the interfacemember 50 may be pushed distally until its travel is stopped by thestent holder 24 and/or the first sheath 20. For example, if the firstsheath 20 is currently in its open position, the interface member 50 mayadvance until its travel is stopped by the stent holder 24. Thereafter,when the first sheath 20 is closed, the interface member 50 maycooperate with the open end 20 b of the first sheath 20 as explainedabove.

Optionally, the interface member 50 may be dimensioned at one end, orboth ends, to be partly insertable into a respective open end of asheath even when the expandable portion 52 (for example, intermediatethe ends) is expanded and is oversize with respect to the open ends ofthe sheaths. Such insertion can provide positive engagement andcooperation between the (or each) sheath and the inter-face member. Suchinsertion can also provide a degree of self-alignment or self-centringbetween the (or each) sheath and the interface member. If both ends ofthe shuttle insert into respective sheaths, the sheaths may alsoself-align or self-centre in register with each other.

Additionally or alternatively, the expandable portion 52 of theinterface member 50 may have a generally smooth annular bulge, or bulb,shape. The expandable portion may have generally rounded or rampsurfaces at its opposite axial ends. Such a shape or shapes may providea smooth transition between the interface member 50 and each open end 20b and 22 b, and/or a generally smooth profile or bridge between the openends 20 b and 22 b. The shape may further enhance self-alignment orself-centring of the open ends 20 b and 22 b in register with eachother.

The expandable portion 52 may be dimensioned such that, in the expandedstate of the expandable portion 52, at least one of the open ends 20 band 22 b will not pass entirely over the expandable portion. Forexample, in the case of confronting open ends 20 b and 22 b, optionallyneither open end 20 b and 22 b may pass entirely over the expandableportion 52. In the case of lapping open ends 20 b and 22 b, optionallyone of the open ends may pass over the expandable portion 52.

The ends of the interface member may be generally asymmetric. In theillustrated form, the proximal end 62 may be formed as a cone. The coneshape may provide a mounting surface for an optional skirt 60 describedbelow, and/or provide a nesting profile to fit the within the third tubecoupling 44. The distal end 64 may be formed as a generally annular rimwith a smooth, e.g. rounded, edge for guiding the open end 20 b of thefirst sheath 20 as the first sheath 20 is closed thereover.

Referring to FIG. 21, in some embodiments, instead of closing thesheaths 20 and 22, it may be desired to remove the catheter 12 from thebody while the distal portion 14 remains in an “open” condition. Forexample, at least the first sheath 20 may remain “open”, whether or notthe second sheath 22 is left “open” or is at least partly closed. Insuch case, the stent holder 24 and the interface member 50 may remainexposed at the distal portion 14. The interface member 50 may tend toslide towards the stent holder 24, either as a result of movementthrough the anatomy, or when the distal portion reaches the site of aclosely fitting introducer 19. The interface member 50 may cooperatewith the stent holder 24 to provide a more streamlined profile than theabrupt edge 92. In particular, the interface member 50 may comprise aconical surface 62 that defines a smooth ramp profile that will slideover the edge of an introducer 19 to guide the stent-holder 24 into theinterior of the introducer and/or through the haemostasis valve. Theinterface member 50 may comprise an enlarged oversize portion 52 thatacts as a stop to prevent the interface member 50 from passing throughthe introducer until the interface member 50 abuts or engages the stentholder 24. At that point, continued pulling to withdraw the cathetercauses the enlarged portion 52 to collapse slightly, allowing theinterface member 50 and stent holder 24 to pass smoothly through theintroducer. The interface member 50 may optionally be configured to forma snug interference fit over the end of the stent holder 24 so that itremains in intimate contact with the stent holder 24.

The interface member 50 as described above may comprise any suitablematerials, including one or more of: plastics, resiliently compressibleplastics, metal and shape-memory alloys (e.g. nitinol). In theillustrated form, the interface member 50 comprises a generallynon-compressible core member 54 carrying a shell 56 defining theexpandable portion 52. The non-compressible core may, for example, be ofplastics. The core member 54 may be longer than the shell 56, and definethe end profiles 62 and 64 described above. The shell 56 may, forexample, be of metal or shape-memory alloy (e.g. nitinol) to provide awell-defined expanded shape. The expandable portion 52 may comprisesegments defining a cage-like bulge or bulb.

In addition to, or as an alternative to, any or all of the aboveconstructional features, the interface member 50 may optionally comprisea flexible sleeve or skirt 60. The sleeve or skirt 60 may optionally beconstructed as plural petals or segments of material that may overlap ornot overlap, and collectively behave as a sleeve or skirt, and allreferences herein to a skirt are intended to refer also to such petalsor segments. The skirt 60 may be deployable from a folded or collapsedstate to an expanded state. The skirt 60 may be substantially selfexpanding. In the folded/collapsed state, the skirt 60 may be retainedand/or restrained within one of the sheaths 20 and 22. In the expandedstate once the skirt 60 has been released, the skirt 60 may bedimensioned to fit outside the open end 20 b, 22 b or at least one ofthe sheaths 20, 22, respectively. In particular, the skirt 60 may coverat least partly the open end 20 b of the first sheath 20. The skirt 60may be made of any suitable material, for example, flexible plastics. Inone form, the skirt 60 may be cut from a shaped balloon member, forexample, as used in a known balloon catheter. A balloon catheter may beused for valvuloplasty. Such a balloon may be molded in its expandedshape, and a skirt 60 cut from such a balloon may be self-biased towardsthe expanded shape, but also be flexible and easily foldable to acollapsed state. Such a balloon is also designed to be of thin materialhaving atraumatic characteristics.

In the illustrated example, the skirt 60 may be bonded to be an integralpart of the interface member 50. The skirt 60 may be bonded to theproximal cone 62. The cone 62 may provide a suitable divergent surfacefor supporting the natural shape of the skirt 60.

Instead of being slidable, the deployable interface member 50 and/orskirt 60 could be substantially stationary with respect to the stentholder 24. In one example described later, the deployable interfacemember 50 and/or skirt 60 may be mounted on the stent holder 24.

FIGS. 10a-c illustrate different examples of attachment element 68 ofthe stent-valve for engaging different examples of stent holder 24, asillustrated in FIGS. 11-13 and 22. The stent-valve may comprise at leastone attachment element 68, optionally two or three attachment elements68, optionally more. Generally, each attachment element 68 may bedefined by an apex 74 or 76, joining first and second struts 70 and 72that extend from an end of the stent-valve 10. The struts 70 and 72 maybe members defining a lattice or skeletal stent structure of thestent-valve 10. In the case of a lattice, the cell associated with thestruts 70 and 72 may project axially beyond neighbouring cells of thelattice.

In FIG. 10a , the struts 70 and 72 may extend generally linearly to meetat apex 74 defining a generally V-shape. In FIGS. 10b and 10c , the apex76 is slightly different by incorporating a U-shape between the ends ofthe struts 70 and 72. The U-shape may be straight sided (e.g., FIG. 10b) or it may have curved sides (e.g. FIG. 10c ).

Referring to FIG. 11, a two-piece stent holder construction isdescribed. However, it will be appreciated that the stent holder may iddesired by made as a one-piece item. A two-piece example construction ofstent holder 24 may generally comprise first and second parts 78 and 80assembled together. The first part 78 may comprise a hub 82 from whichproject a plurality of projections 84. The second part 80 may comprise acasing having a hollow interior for fitting around at least a portion ofthe hub 82 from which the projections 84 project, and defininginterstices 86 for accommodating the locking projections 84 with a spaceor clearance 88 therearound. The casing may be forked to define theinterstices. The edge 90 of each interstice 86 may optionally be roundedor chamfered. A two-part assembly may enable a complex shape of stentholder 24 to be formed reliably and cost effectively. It may also permitdifferent materials to be used as appropriate (for example, the firstpart may be of metal for strength, and the second part may be ofplastics). However, as already mentioned, the stent-holder 24 may beformed as unitary item instead of an assembly of plural parts.

The projections 84 may be configured for fitting within the interior ofthe apex 74 or 76 of each attachment element 68, when the stent-valve 10is in its collapsed state. The engagement between the projection 84 andthe apex 74/76 traps the attachment element (and hence the stent-valve10) against axial movement, at least in an axial direction away from thestent holder 24.

The projection 84 may be referred to as a radial projection because itgenerally projects in a radial direction. In some embodiments, theprojection, or an edge thereof, may be inclined towards the distaldirection, by an angle of, for example, not more than about 20 degrees,optionally not more than about 10 degrees, optionally not more thanabout 5 degrees.

In the example of FIGS. 11 and 12, the projection 84 has an elongateblade or fin shape, suitable for fitting within the interior of apex 74(FIG. 10a ). Use of a fin or blade can enable the projection 84 to havea desirably thin shape, while remaining strong (especially in the axial,elongate direction). In addition to the projection 84 trapping thestent-valve 10 against axial movement away from the stent-holder, theshape of the interstice 86 cupping the apex 74, and/or engagementbetween an end face 92 of the stent holder 24 and neighbouring cellapexes of the stent, may restrain the stent-valve 10 against axialmovement in the opposite direction. The stent-valve 10 may thereby beretained firmly in position until expansion of the stent-valve 10 maydisengage the or each attachment element 68 from the stent-holder 24.

In the case of a self-expanding stent-valve 10, the attachment elementsmay disengage when the portion of the stent-valve 10 from which theattachment elements 68 extend, is uncovered by a sheath (for example,the first sheath 20). Upon expansion of the stent-valve 10, the struts70 and 72 move apart to open the V-shape of the apex 74. As the V-shapeopens, this enlarges the interior of the attachment element 68 tofacilitate disengagement between the projection 84 and the apex 74. Thechamfered edge 90 of the interstice 86 also acts as a ramp surface to“lift” radially the struts 70 and 72 out of the clearance 88 as thestruts 70 and 72 expand circumferentially and bear against the edge 90.In case the attachment elements 68 may stick accidentally within theinterstice 86, the attachment elements 68 may be freed by slightrotation and/or axial displacement of the catheter, to promote furtherriding against the edge 90.

In the example of FIGS. 13 and 22, the projections 84 are fingers orpins, suitable for fitting within the interior of apex 76 (FIGS. 10b/c). Each pin (FIG. 13) may have a larger thickness than an equivalentfin (FIG. 12). In a collapsed condition of the stent-valve 10 (FIG. 13),the struts 70 and 72 may lie closely adjacent each other at theattachment element 68, such that the arc of the U-shape portion 76extends around a first angle more than 180 degrees to define a closed ornear closed eyelet having an aperture larger than the spacing of thestruts, to accommodate the pin 84. The U-shape may be referred to as ahorseshoe U-shape. The eyelet aperture and space between the struts maytogether define a keyhole type shape. Alternatively, the struts 70 and72 may bear against each other at the attachment element 68 to close theeyelet. Either arrangement can restrain the attachment element 68 inboth axial directions, merely by engagement between the attachmentelement 68 and the projection 84. This may be advantageous by enabling alarger chamfer surface to be used at the edge 90 of the interstice 86and/or at the end face 92 of the stent-holder. A chamfered end face 92may be desirable to facilitate withdrawal of the stent holder 24 andfirst sheath 20 through the stent-valve 10 once implanted.

In the expanded (or functional or non-collapsed) condition of thestent-valve 10 the struts 70 and 72 may move apart, and the arc of theU-shape apex 76 may extend around a second angle that is less than thefirst angle, to at least partly open the eyelet. The second angle may beabout 180 degrees or less. For example, the apex may have asubstantially straight-sided U-shape. In a similar manner to thatdescribed above, opening of the apex 86 may facilitate disengagementfrom the projection 84. The chamfered edge 90 of the interstice 86 alsoacts as a ramp surface to “lift” radially the struts 70 and 72 out ofthe clearance 88 as the struts 70 and 72 expand circumferentially andbear against the edge 90.

FIG. 22 shows a stent holder equivalent to FIG. 13, optionally forproduction as a single-piece item. All of the stent holders illustratedin FIGS. 11-13 and 22 illustrate the provision of at least one rampsurface extending partly around each projection, to define ramp surfaceportions circumferentially either side of the projection and axially(e.g. distally) to one side of the projection. The ramp surface portionsare inclined outwardly away from the projections. The clearance aroundthe projection is open to the other axial (proximal side) and/or openradially outwardly. The radial height of the projection 84 may beaccommodated entirely or at least substantially within the profile ofthe stent holder body. The stent holder body may be a surface ofrevolution. One difference that may be noted between on the one hand theexample of FIGS. 11 and 12, and on the other hand the examples of FIGS.13 and 22, is that in the latter example, the ramp surface extends tothe floor of the clearance or interstice around the projection 84. Theramp surface may generally be inclined at an angle of between about 20and about 40 degrees, optionally around 30 or 35 degrees.

Referring to FIGS. 14 and 23, the stent-holder 24 may carry a skirt (ormay also be referred to as sleeve) 94. The skirt 94 may optionally beconstructed as plural petals or segments of material that collectivelybehave as a sleeve or skirt, and all references herein to a sleeve/skirtare intended to refer also to such petals or segments. The skirt 94 maybe similar to the skirt 60 described above, and the same constructionaldetails may be used. FIG. 23 illustrates one example structure in moredetail. The skirt 94 may comprise a generally tubular sleeve section 94a and a plurality of cuts or slits 94 b defining joined petals orsegments 94 c. The petals 94 c may substantially cover the projections84 and/or the radial recess therearound. The slits 94 b may permit thepetals 94 c to fold or flex outwardly open. The slits 94 b may bealigned generally with the projections 84 or the radial recessestherearound. Such positioning of the slits 94 b can ensure that thepetals 94 c do not obstruct expansion and detachment of the attachmentelements of the stent-valve. Outward flexing of the petals mayautomatically cause the slits 94 b to open, to allow the attachmentelements to expand through the open slits.

The skirt 94 may function to facilitate loading of the collapsedstent-valve 10 into especially the first sheath 20, prior to use of thedelivery catheter 12. Loading may be achieved by first opening the firstsheath 20 (arrow 20 a), folding back or open the skirt 94 (or the petals94 c thereof), collapsing the stent-valve 10 such that the attachmentelements 68 engage in the stent-holder 24, and then moving the firstsheath 20 its closed position (arrow 20 c) covering the distal portionof the stent-valve 10. The skirt 94 may return flat to cover, at leastpartly, the attachment elements 68. Covering the attachment elements 68may avoid the apex 74 or 76 creating an abrupt edge that obstructsclosing of the first sheath 10, if the attachment element 68 is notperfectly flush with the surface of the stent holder 24. Covering theattachment elements 68 may also avoid one of the attachment elementsaccidently passing outside the open end 20 b of the first sheath 20. Itwill be appreciated that, when the stent-valve 10 comprises pluralattachment elements 68, it may be difficult to see whether all of theattachment elements 68 are engaged perfectly into the stent holder 24during loading. Covering the attachment elements 68 with the skirt 94may reduce this problem, and may compensate to guide the open end 20 bof the first sheath 20 over the attachment elements 68 even if notperfectly positioned. The skirt 94 may also protect the open end of thefirst sleeve 20 from rubbing aggressively on the edge of outer skirtmaterial of the stent-valve.

The skirt 94 on the stent holder may also find use in a deliverycatheter 12 that has only a single sheath (not shown).

In the arrangement of FIG. 14, the skirt 94 may be distinct from theoptional skirt 60 of the separate interface member 50. FIG. 15 mayillustrate an alternative arrangement in which a single sleeve or skirt94 may additionally perform the function of skirt 60 as an interfaceelement.

Referring to FIG. 15, following release of the stent-valve 10, the skirt94 may be directed with its open end facing distally, in order to coverthe open end 20 b of the first sheath 20. The skirt 94 may extendoutside the first sheath 20. Within the terminology of an interfacemember, the skirt 94 may be in a deployed state when extending outsidethe first sheath 20. The second sheath 22 may be advanced distallytowards the first sheath 20. The second sheath 22 may optionally beadvanced distally beyond its normal closed position.

Additionally or alternatively to the skirt 94, it will be appreciatedthat other deployable interface elements may be provided on, or formpart of, the stent holder 24, or be mounted on the stent holder supporttube. This would illustrate a further example of a deployable interfaceelement that is not freely slidable within the accommodation region 18.

FIG. 16 illustrates a handle 100 for the proximal portion 16 of thedelivery catheter, for controlling the distal portion 14 via the tubes26-30 extending between the proximal and distal portions of the deliverycatheter. The tubes 26 may optionally include or be connected torespective rigid portions that extend through the handle 100.

The handle 100 may comprise a fixed body 102 which extends substantiallythe length of the handle 100, and may have an elongate slot 104 throughwhich control pins can slide, as described herein after. A fixing 106may fixedly couple the body 102 to the first tube 26, such that the body102 may control the relative position of the first tube 26. A grippable“first tube” handle 108 may be coupled to the body 102, for example, atthe distal end of the handle 100.

The handle 100 may further comprise a “second tube” handle 110 having ahelical guide 112 associated therewith. The helical guide 112 mayoptionally be formed in a separate component 112 a that is coupled torotate with the “second tube” handle 110. A slider 114 coupled to thesecond tube 28 may have a pin 116 that extends through the slot 104 intoengagement with the helical guide 112. The “second tube” handle 110 maybe rotatable about the body 102. Rotation of the “second tube” handle110 (relative to the body 102) rotates the helical guide 112, causingthe pin 116 and hence the slider 114 to move axially. The slider 114transmits the axial movement to translate the second tube 28 relative tothe first tube 26, thereby to translate the first (distal) sheath 20with respect to the stent holder 24.

The handle 100 may further comprise a “third tube” handle 118 having ahelical guide 120 associated therewith. The helical guide 120 mayoptionally be formed in a separate component 120 a that is coupled torotate with the “third tube” handle 118. A slider 122 coupled to thethird tube 30 may have a pin 124 that extends through the slot 104 intoengagement with the helical guide 120. The “third tube” handle 118 maybe rotatable about the body 102. Rotation of the “third tube” handle 118(relative to the body 102) rotates the helical guide 120, causing thepin 124 and hence the slider 122 to move axially. The slider 122transmits the axial movement to translate the third tube 30 relative tothe first tube 26, thereby to translate the second (proximal) sheath 22with respect to the stent holder 24.

Optionally, the handle 100 may comprises at least one flushing port 126through which liquid (e.g. saline) may be injected, in order to flushair from spaces that are open to the anatomy. In particular, it may bedesired to flush the space between the first and second tubes, and thespace between the second and third tubes. In some embodiments, a singleor common flushing port 126 may be provided for flushing both spaces. Acommunication port or aperture (the position of which is indicatedschematically at 128 and referred to hereinafter by the same numeral)may be provided for allowing liquid in one space to enter the other. Forexample, the flushing port 126 may be configured to admit liquid intothe space between the first and second tubes. A communication port 128in the second tube may permit the liquid also to enter the space betweenthe second and third tubes. The communication port 128 is optionallypositioned at the handle 100, or at least closer to the proximal portionof the catheter than to the distal portion, in order to flush the spacesthoroughly to the distal portion. Provision of a single or commonflushing port 126 for flushing plural spaces may be advantageous insimplifying the number of connections and operations that an operatorhas to perform when preparing the catheter for use. Alternatively, if itis desirable to have independent control over flushing of each space,plural flushing ports 128 may be provided, each communicatingindividually with a respective space to be flushed.

The handle 100 may be configured to apply pre-tension to one or more ofthe tubes, as described above. Various mechanisms for applyingpre-tension are envisaged. The mechanism may be part of the “secondtube” handle 110, or it may be a separate mechanism capable of applyingtension. In a simple, yet effective and intuitive form, the “secondtube” handle 110 may be rotatable to generate pre-tension, and may belockable in the tensioning position. The handle may be lockable usingany suitable locks, such as a removable pin, or a ratchet mechanism.Additionally, the handle 100 may include an indicator ring forindicating the amount of rotation of the handle 110 to generate adesired amount of pre-tension. The indicator ring may be manuallysettable such that a first marker is in register with a counter-markeron the handle 110 when the first sheath is in a closed position withoutpre-tension. Once set, the indicator ring may indicate, by a secondmarker, the degree of further rotation by which the handle 110 should beturned or displaced to generate the pre-tension. The lock for lockingthe handle 110 in position, and/or the settable indicator ring, aregenerally indicated schematically at 110 a. However, it will beappreciated that the lock and indicator ring may be separated and/orplaced at different positions on the handle 100 as desired.

FIG. 20 illustrates a liner sleeve 150 that may be used with thecatheter 12. The liner sleeve 150 may act as a friction reducing linerbetween the catheter 12 and an introducer 19 (for example, a standardarterial introducer) through which the catheter is inserted into thebody. The liner sleeve 150 may reduce friction on the catheter tubes,especially the outer tube 30, permitting easier deployment of the stent10. A standard arterial introducer includes a haemostasis valve 19 a forpreventing blood reflux and air aspiration. The haemostasis valve 19 amay be a quite aggressive multiple flap valve in order to function witha wide range of different equipment types and sizes that could beintroduced into the artery. The aggressiveness of the haemostasis valvemay tend to obstruct fine displacement of the tubes of the deliverycatheter 12 for controlling translation of the sheaths at the distalportion. The liner sleeve 150 provides a low friction interface betweenthe third tube 30 and the introducer 19. The liner sleeve 150 may becaptive on the catheter 12, and slidable axially along the catheterlength. The liner sleeve 150 may include, at its proximal end, a stop152 that limits the extent of entry into the introducer. Additionally oralternatively, the liner sleeve 150 may include a portion 154 forremovable interference fit with a socket 156 of the handle 100. Thispermits the liner sleeve 150 to be stowed connected to the socket 156 ofthe handle 100, and separated from the handle 100 when desired toadvance the liner sleeve 150 into operative position within anintroducer 19. The liner sleeve 150 may optionally additionally comprisea seal 158 for effecting a substantially blood-tight seal between theliner sleeve 150 and the outer tube 30 of the catheter 12. The seal 158may be configured uniquely for the dimension of the catheter 12, and somay be substantially less aggressive than the haemostasis seal 19 a ofthe introducer 19. For example, the seal 158 may be formed by an O-ring.The seal 158 may optionally be provided at the stop 152 or the connector154, such that the seal 158 is not subjected to the forces within theintroducer 19. Alternatively, the seal 158 may be positioned elsewherealong the length of the liner sleeve 150.

When deployed into the introducer, the liner sleeve 150 may not be fixedaxially and/or rotationally with respect to the remainder of thecatheter 12, allowing the catheter to be manipulated withoutobstruction. In some embodiments, the length of the liner sleeve 150projecting distally from the stop 152 may be not be greater than about30 cm, optionally not greater than about 25 cm, optionally not greaterthan about 20 cm, optionally not greater than about 15 cm, optionallynot greater than about 10 cm.

FIG. 24 illustrates a modification of the delivery catheter including aball joint (the terms ball joint, ball socket, ball socket articulation,and ball socket connection are all interchangeable) in at least onetubular member of the catheter. The ball joint may be provided justproximal to the stent accommodation region (also referred to herein asstent-holding region or compartment) of the catheter, such that the balljoint can provide a high-flexibility region just proximal to thestent-holding compartment. The ball joint can be within 5 cm proximal ofthe stent holding compartment. The ball joint can also be 0.1, 0.5, 1,2, 3, 4 or 4.5 cm proximal of the stent holding compartment. The balljoint can also be between 1 and 2 cm proximal of the stent holdingcompartment. The ball joint may be provided in a tubular member of thecatheter that moves axially with respect to the position of the stent.That is, the tubular member, according to so-me embodiments, can bemoved in a proximal 22A or distal 20A direction (also as shown inFIG. 1) to release the stent. In this case, the distance measurementabove is defined to be when the tubular member is in a positioncorresponding to a closed position, e.g. a most closed position for thattubular member. An example of this closed position is shown in FIG. 24.In the closed position, the sheaths may meet end to end, or remainspaced from each other.

The ball joint may be provided in the outer tubular member of thecatheter assembly. The ball joint is preferably hollow or includes anaperture to permit passage of one or more inner tubular members. In someembodiments, there is a single inner tubular member that passes throughthe outer tubular member. This inner tubular member can be a guide-wirereceiving lumen. Also a stent holder can be mounted on this innertubular member. There can also be at least two tubular members that passthrough the outer tubular member. These two or more inner tubularmembers can be arranged one within the other. There can also be three,four, five, six, seven, eight, nine or ten inner tubular members. Eachof these can be nested within each other.

In some embodiments, the ball joint can allow bending of the tubularmembers through a range of up to at least 45°, compared to thestraight-axis of the catheter at that point. The ball joint can alsoallow bending of the tubular members of up to at least 40°, compared tothe straight-axis of the catheter at that point. The ball joint can alsoallow bending of the tubular members of up to at least 30°, compared tothe straight-axis of the catheter at that point. The ball joint can alsoallow bending of the tubular members of up to at least 20°, compared tothe straight-axis of the catheter at that point. The ball joint can alsoallow bending of the tubular members through 20°, 21°, 22°, 23°, 24°,25°, 26°, 27°, 28°, 29°, 31°, 32°, 33°, 34°, 35°, 36°, 37°, 38°, 39°,41°, 42°, 43° and 44°, compared to the straight-axis of the catheter atthat point. Such high flexibility would be difficult to achieve with acontinuous bending member of equivalent cross-section diameter, withoutrisk of kinking the continuous member.

In some embodiments, the ball joint has a transverse outer diameter(e.g., measured in a cross-section direction to the axis of thecatheter) that is not greater than a diameter of at least one adjacenttubular member of the catheter assembly. This enables the ball-joint tobe accommodated without enlarging the size profile of the catheterassembly. The profile of the tubular member adjacent to the ball jointmay blend smoothly into the profile of the ball joint, to define agenerally smooth continuous surface, even when the catheter assembly isflexed at the ball joint. If desired, the transverse outer diameter ofthe ball joint may be larger than the a diameter of both adjacenttubular members of the catheter assembly leading to the ball joint.

In some embodiments, the transverse outer diameter of the ball joint isnot greater than a largest tubular member diameter of the catheterassembly. For example, for a catheter assembly insertable into the bodyusing an introducer of 18 French size, the maximum diameter of an outertubular member is approximately 6 mm (not greater than 7 mm). Thetransverse outer diameter of the ball joint might then be no larger thanthis maximum diameter. In some embodiments, the length of the ball joint(in an axial direction of the catheter assembly) may be up to about twothirds of the transverse outer diameter of the ball joint.

In some embodiments, the ball joint can also allow an axial force to beapplied along the length of the tubular members, for pushing forward(distally) or drawing back (proximally) the tubular members. Forexample, the outer tubular member may comprise a sheath (e.g. proximalsheath part) that at least partly encompasses the stent, and the sheathmay translate axially forwards or backwards under the axial force toshift from a closed state to an open state. The axial force may beapplied through the ball joint. The ball joint can thus form part of aportion or sub-assembly of the catheter that moves axially with regardsto the stent position on the catheter.

In some embodiments, the ball joint can also allow relative rotationbetween the two parts of the tubular members on either side of the balljoint. The relative rotation may be limited up to one turn, or in someembodiments, the relative rotation may also be limited up to two, three,four, five, six, seven, eight, nine or ten turns. Alternatively, it maybe unlimited. Either arrangement may enable the stent-holdingcompartment of the catheter to be rotated, while the outer body of thecatheter remains stationary in the artery without rotation. The outerbody of the catheter can act like a bushing within which the othertubular members turn, without friction with regards to the artery wall.The torsion can be applied via the other (one or more) tubular memberscarried within the catheter and passing through the ball joint to thedistal section of the delivery device (at least distal of the balljoint). Alternatively, a hydraulic or electronic actuator may generaterotary movement at the distal part (stent-holding compartment) inresponse to a suitable fluid/electronic signal supplied via a electronicsignal line or a fluid conduit.

FIG. 24 presents an example of a stent delivery device with a ball jointaccording to some embodiments of the present disclosure. As shown, balljoint 1 is provided in the outer tubular member 30 of the catheter,which is the tubular member for drawing back (proximally 22A towards thecatheter handle) the proximal outer sheath (second sheath) 22 thatcovers (at least) a portion of the stent 10. For pulling back theproximal sheath, an axial force is applied from a handle along thecatheter length, and then through the ball joint to the outer sheath.Rotation is achieved by applying a torsional force to inner tubularmembers 26 and/or 28 within the catheter. These turn the stent fromwithin. The stent holder 30 transmits the torsional force from the otherinterior tubular members to rotate the stent about the catheter axis.The friction between the stent and the outer sheath also turns the outersheath. The ball joint enables the outer sheath to turn freely withouttorsion being applied to (or resisted) by the body of the catheter. FIG.1 also shows that the stent holder can be located distally 6A orproximally 6B. The stentholding compartment is made up of the proximalsheath 22 and the distal sheath 20. The distal sheath is attached to theinner tubular members. When the inner tubular members are extendeddistally, the distal sheath can also be pushed distally and off of thestent. Likewise, the proximal sheath can be pulled proximally, asdescribed above. The inner most tubular member also forms a guidewirelumen 3 that extends through the center of the catheter.

The ball joint and the portions of the tubular member coupled theretomay be of any suitable material, e.g. metal (e.g. stainless steel) orplastics (e.g. nylon).

The socket part of the ball joint may communicate with a stepped-down,or even necked-down, region of the tubular member, in order to allow thespherical extent of the socket surface to be increased.

A related aspect may be to provide a high-flexibility portion of thecatheter adjacent to the stent-holding compartment. The high-flexibilitymay be defined as having a bending resistance less than 50% of thetubular member on either side of the high-flexibility region. The highflexibility region may also have a resistance of 10%, 15%, 20%, 25%,30%, 35%, 40% or 45% of the tubular member on either side of thehigh-flexibility region. The high-flexibility region may have an axiallength of less than 5 cm. The high-flexibility region may also have anaxial length of between 1 and 2 cm. One implementation for thehigh-flexibility region may be using a ball joint as above. Another maybe to use a segment of high-flexibility tubing joined to (or integralwith) the catheter tubing.

The flexing and rotary articulation of a ball joint may even beseparated into two separate connections, joints or couplings, providedthat both of these are close to the stent-holding compartment of thecatheter. The two couplings are generally not more than 5 cm apart. Thetwo couplings can also be between 1 and 2 cm apart. The flexingconnection can be positioned closer to the stent-holding compartment tocompensate for the rigidity of the adjacent stent, but the order couldeasily be reversed according to a particular implementation.

It will be appreciated that including a ball joint in the outer tube mayrestrict the amount of torque transmittable through the outer tube. Theconstruction of other inner tubes may optionally be modified to transmittorque, for example, using the principles described previously.

FIGS. 17, 18 and 19 illustrate a detailed example of a stent-valve 10for which the delivery catheter 12 of any of the preceding embodimentsmay be eminently suitable. The stent-valve 10 may be of a self-expandingtype that is resiliently biased towards the expanded and/or functionalstate, and is compressible to a compressed state by application ofsuitable radial compression forces. The stent-valve 10 remains in itscompressed state while constrained. When the constraint is removed, thestent-valve 10 self expands towards the expanded and/or functionalstate. Alternatively, the stent-valve 10 may be of a non-self-expandingtype that requires application of an expansion force to transform thestent-valve 10 from the compressed state 10′ to the expanded state.

The stent-valve 10 may comprise a stent component 134 supporting aplurality of valve leaflets 136. The leaflets 136 may collectively bereferred to as a valve component, whether or not the leaflets 136 forman integral unit. The stent component 134 may provide an anchoringfunction for anchoring the stent-valve in the native anatomy and/or asupport function for supporting the valve leaflets 136. The stentcomponent 134 may be of any suitable material or materials. The stentcomponent 14 may be of metal. Example materials include shape memoryand/or superelastic alloys (for example, nitinol), stainless steel, orcobalt-chromium alloy. In the illustrated form, the stent component 134is self-expanding and is of shape memory/superelastic alloy (e.g.nitinol). However, the stent component 134 could also be substantiallynon-self expanding.

The stent component 134 may have any profile desired for anchoringand/or aligning the stent-valve 10 with respect to the native anatomy atthe desired implantation site. In some embodiments, the stent component134 may be generally cylindrical in shape, or comprise one moregenerally cylindrical portions or portions lying on a generallycylindrical surface (e.g. 140 c and 142 a). Additionally oralternatively, the stent component 134 may be generally non-cylindricalin shape or comprise one or more generally non-cylindrical portions orportions lying on a non-cylindrical surface (e.g. 140 a, 140 b, and144). Additionally or alternatively, the stent component 134 maycomprise one or more anchor projections, and/or one or morestabilization portions.

Viewed in one aspect, the stent component 134 optionally has an inflowend and an outflow end, optionally is self-expandable from a compressedstate for delivery towards a functional state upon implantation, thestent component 134 comprising an outflow structure, for example, in theform of a plurality of arches 144 a at the outflow end each having anapex at the outflow end, the stent component further comprising a crown(e.g. superior crown) 140 b intermediate the inflow and outflow ends,the crown 140 b having a free extremity intermediate the inflow andoutflow ends and directed towards the outflow end, and thestent-component further comprising a fixation section (e.g. inferiorcrown) 140 a between the crown and the inflow end.

Additionally or alternatively, the stent component 134 optionallycomprises an anchoring portion 140 defined, for example, by an inferiorcrown 140 a and a superior crown (or other fixation section) 140 b thattogether define a groove and/or waist 140 c therebetween. The anchoringportion 140 may have a first resistance to compression, and may comprisea cellular lattice.

The stent component 134 optionally (further) comprises a valve supportportion 142 comprising, for example, a plurality (e.g. three)commissural support posts 142 a. The commissural support posts 142 a maybe arranged on a pitch circle diameter smaller than an extremity of atleast one of the crowns 140 a and 140 b. The commissural support posts142 a may be arranged on a pitch circle diameter corresponding to thewaist 140 c. The commissural support posts 142 a may partly overlap atleast one of the crowns 140 and 142 in the axial direction, and extendaxially beyond that respective crown. The commissural support posts 142a may be frame-like. The commissural support posts 142 a may have ashape that follows, at least approximately, a peripheral contour of thevalve, at least in the region of the valve periphery adjacent to thecommissural support posts.

The stent component 134 optionally (further) comprises a stabilizationor alignment portion 144 which may represent an outflow structure. Theportion 144 may be defined, for example, by a plurality (e.g. three)wings or arches 144 a. The arches 144 a may extend from tips of thecommissural support posts 142 a, to define a vaulted structurethereover. The alignment portion 144 may have a greater flexibility thanthe anchoring portion 140 and/or the valve support portion 142. Thealignment portion 144 may have a second resistance to compression thatis smaller than the first resistance to compression of the anchoringportion 140. The alignment portion 144 may be less rigid (e.g. radially)than the anchoring portion 140 and/or the valve support portion 142.

The stent component 134 optionally (further) comprises an attachmentelement 68 for attaching the stent component 134 to a stent holder 24 ofthe delivery catheter 12. In the present embodiment, the attachmentportion 68 is defined by a plurality (e.g. three) of extensions of cellsof the inferior crown 140 a, and have a shape corresponding to one ofthe examples of FIGS. 10a -c.

The valve component or leaflets 136 may be of any suitable naturaland/or synthetic material(s). For example, the valve component/leaflets136 may comprise porcine and/or bovine pericardium and/or harvestednatural valve material. The leaflets may be supported to coapt orcollapse to a closed position to obstruct flow in one directiontherepast, while flexing apart to an open position to allow flow in anopposite direction. The valve component/leaflets 136 may be accommodatedat the valve support portion 142 and/or at least partly within theanchoring portion 140. The leaflets may have side tabs. The tabs ofadjacent pairs of leaflets may pass in pairs through slots in thesupport posts 142, be folded back and sutured on either side of theslot. The support posts 142 a may have lines of suture holes either sideof the slot to accommodate the sutures. Further suture holes may beprovided above and/or below the slots. If desired the suture hole abovethe slot (indicated at A in FIG. 19) and/or the suture hole below theslot, may be omitted to save space.

The stent-valve 10 (e.g. the valve component 136) may further comprisean inner skirt and/or an outer skirt covering at least partly arespective inner or outer surface portion of the stent component 14. Forexample, the skirt(s) may cover at least a portion of the anchoringportion 140 and/or at least a portion of the valve support portion 142.The skirt(s) may be made of any suitable material, including PET and/orpericardium. The pericardium may be of the same material as theleaflets. In some embodiments, the inner and outer skirts may partlyoverlap each other in a skirt overlap region A in FIG. 17, and includenon-overlapping portions extending axially above and below,respectively, the overlap region A. The inner skirt may be advantageousin channel blood towards the leaflets and preventing leakage of bloodthrough the interstices of the lattice structure. The outer skirt may beadvantageous in preventing leakage of blood at the interface between thestent-valve and surrounding tissue. Providing both skirts, but with onlypartial overlap, may enable the advantages of both to be obtained, butalso reducing full overlap of material (which would otherwise increasethe thickness of material of the stent-valve, making it more difficultto compress the stent-valve to a small size). The partial overlapnevertheless enables a reliable seal to be achieved between the innerand outer skirts.

In use, viewed in one general aspect, at least a portion of the inferiorcrown (or other fixation section) 140 a may be received and constrainedby the first sheath 20. At least a portion of the stent-component 134not covered by the first sheath 20 may be received and constrained bythe second sheath 22. As explained earlier and described in more detailbelow, a method of releasing the stent-valve 10 may include moving thesecond sheath 20 to an open position in order to deploy thecrown/superior crown 140 b, followed by the support section 142, andfinally the arches 144 a. For example, these elements may be deployed onan aorta side of a native and/or failed valve. Thereafter, once theoperator is satisfied with the position and/or function of thestent-valve 10 within the native anatomy, the first sheath 10 may bemoved to its open position in order to deploy the inferior crown 140 a.Simultaneously, the attachment elements 68 may release from thestent-holder 24.

Such a deployment sequence is different from that described in theaforementioned WO-A-2009/053497 and WO-A-2011/051043. Nevertheless, ithas been appreciated that deploying the arches 144 a after the crown 140b is still highly effective in permitting the arches to function.Notably, the arches may be deployed prior to uncovering of the fixationsection 140 a for deployment.

In some embodiments, the arches may be configured for aligning thestent-valve with respect to an axis of the ascending aorta by contactwith a wall of the ascending aorta. For example, the arches may bebendable independently of each other. The crown may be configured forengaging and/or seating against existing leaflets from an outflow side.The fixation section may be configured for engaging an existing annulus.

Deploying the arches before the fixation section may permitself-alignment of the stent-valve by the action of the arches, beforethe fixation section deploys to anchor the stent-valve at the annulus ofthe existing valve.

There now follows a detailed description of how the apparatus describedabove may be used in one example. The description may be modifiedaccording to which features of the apparatus may be implementedaccording to the actual embodiment used. The order of the individualsteps may be changed as desired. The steps are grouped by topic. Theorder of the topics may be changed as desired. The order of steps withineach topic may be changed as desired. The following description mayfocus principally on features of the delivery catheter previouslydescribed; additional steps not described here may be included as partof the procedure, as may be known to practitioners in the field oftranscatheter stent-valve implantation.

-   A: Loading of the stent-valve into the accommodation region:

A1: The first and second sheaths 20 and 22 are each translated open byusing the controls 110 and 118 of the handle 100. The petals 94 c of theskirt 94 are folded back to expose the projections 84 of the stentholder.

A2: The stent-valve 10 is compressed in place in the accommodationregions. A conventional crimper may be used. The stent-valve is arrangedwith its end (for example, inflow end) having the attachment elementspositioned distally in the accommodation region, and in register withthe projections 84. The fixation section/inferior crown 140 a may becompressed first, such that the attachment elements 68 mate with theprojections 84. Using the handle 110, the first sheath 20 may betranslated proximally to at least partly cover the fixationsection/inferior crown 140 a, and capture the stent-valve by itsattachment elements. During such translation, the petals 94 may unfoldflat to lie between the interior surface of the first sheath 20, and anexterior surface portion of the stent-valve. Next the remaining sectionsof the stent-valve may be compressed (e.g. the crown/superior crown 140b; the valve support section; and the arches) and the second sheath 22is translated distally to at least partly cover the stent-valve from thearches to the crown/superior crown 140 b to constrain these sections ofthe stent-valve compressed. As mentioned previously, in the closedpositions of the first and second sheaths, the ends of the sheaths maymeet substantially end to end, or the sheaths may remain spaced apart.

-   B: Preparation of the delivery catheter for introduction into the    body (following steps A):

B1: The delivery catheter may be flushed by injecting liquid (e.g.saline) via the at least one flushing port 126. Optionally, pluralspaces within the delivery catheter may be flushed by injecting liquidthrough a single and/or common port 126.

B2: The first tube 26 may be pre-tensioned by rotating the second tubehandle 110 to “overclose” the first sheath. The amount of pre-tension toapply may be indicated by manually setting the indicator ring such thata first marker on the indicator ring aligns with a counter-marker on thehandle 100. The second tube handle 110 is further rotated manually by anamount indicated by a second marker on the ring to generate thepre-tension. The second tube handle 100 may optionally be locked in thepre-tensioning position, in order to avoid the handle slipping in useand relaxing the pre-tension before the moment intended.

-   C: Steps carried out on the patient prior to implantation (following    steps A or B):

C1: An arterial introducer 19 is placed to penetrate percutaneously anartery, for example, the femoral artery or the subclavian artery. Aguide wire is introduced through the introducer 19 and navigated alongthe vasculature to traverse the valve to be replaced, for example, anaortic valve.

C2: A balloon catheter may optionally be introduced through theintroducer 19 and advanced along the guide wire to the valve to bereplaced. Valvuloplasty may be performed to free the valve leaflets inthe case of a stenosed valve. The balloon catheter is then removed.

-   D: Stent-Valve Implantation (following steps A, B and C):

D1: The delivery catheter may be fed over the guidewire towards theintroducer 19, with the guidewire being received within the lumen of thefirst tube 26. The distal portion of the delivery catheter may beintroduced through the introducer. Thereafter the delivery catheter maybe fed progressively through the introducer, to advance the distalportion along the guidewire to the location of the valve to be replaced.

D2: At some stage, at least after the distal portion has passed throughthe introducer 19, the liner sleeve 150 may be separated from the handle100, and slid distally along the catheter stem and into the introducer19 to provide a reduced friction fit in the introducer. This may permiteasier advancement of the catheter through the vasculature, and/or easymanipulation of the sheaths at the following steps.

D3: When the distal portion is approximately in position, or slightlyhigh in the ascending aorta, the operator may, if desired, rotate thedelivery catheter, to rotationally align the stent-valve with the nativeanatomy. Although the geometry of the stent-valve itself may not requiresuch rotational alignment, some practitioners may prefer the possibilityto align the stent-valve with the native valve, such that thestent-valve can replicate the natural valve function as closely aspossible. As described previously, the combination of the braided tubes26 and 30, and/or the braid characteristic of the third tube 30, permitsgood transmission of torque from the handle 100 to the distal portion,despite the relatively long length of the delivery catheter. Therotational orientation of the stent-valve may be observed using suitableimaging equipment, for example, X-ray imaging equipment.

D4: With the distal portion still approximately in position, or slightlyhigh in the ascending aorta, the third tube handle 118 may be operatedto translate the second sheath 22 proximally, and release the sectionsof the stent-valve previously covered by the second sheath 22. This mayinclude the crown/superior crown 140 b, the arches 144 a, and any stentsections in between (e.g. the support section 142). The translation ofthe second sheath 22 may release first the crown/superior crown 140 b,followed last by the arches 144 a. If pre-tension is used in step B2,the pre-tension may bias the first sheath proximally preventing anytendency for the first sheath to creep distally as a result of thereaction forces applied though the tubes during the manipulation of thesecond sheath. It may be appreciated that although the pre-tensioningstep is described as part of the preparation at step B2, the applicationof pre-tension may be performed later at any stage before D4, even afterthe catheter has been advanced to the valve to be replaced. Performingthe pre-tensioning step later may, in some cases, improve theflexibility of the catheter for tracking along the guidewire.Additionally or alternatively, it may be appreciated that if the linersleeve 150 if used at step D2, the liner sleeve 150 may reducesfrictional resistance against movement of the third tube 30 within theintroducer 19, thereby making the operation of translating the secondsheath 22 easier and smoother.

D5: The operator may push the catheter gently until the deployedcrown/superior crown 140 b bears against the existing leaflets of thevalve to be replaced. Upon such placement, the operator may feelresistance, and effectively feel that the crown/superior crown 140 b isseated correctly against the leaflets. Additionally or alternatively,the position may be monitored by suitable imaging equipment, such asX-ray imaging equipment. During such manipulation of the catheter withthe stent-valve partly deployed, the engagement between the stent holder24 and the attachment elements 68 keeps the stent-valve firmly anchoredto the delivery catheter.

D6: When the operator is satisfied about the position of thecrown/superior crown 140 b, the operator may operate the second tubehandle 110 to translate the first sheath 20 distally in order to releasethe fixation section/inferior crown 140 a. If the second tube handle 110has been locked in position as part of the pre-tensioning operation, thelock may be removed or disengaged to allow the pre-tension to berelaxed, and the second tube instead to apply a compression force fortranslating the first sheath distally. As mentioned previously, theconstruction of the second tube 28 provides good column strength fortransmitting the compression force from the handle 100 to the firstsheath 20.

D7: Upon removal of the first sheath 20, the fixation section/inferiorcrown 140 a deploys to anchor the stent-valve in position. Theattachment elements 68 expand radially outwardly and may expandcircumferentially, to release automatically from the projections 84 ofthe stent holder 24. The ramp surfaces at least partly surrounding theprojections 84 lift the expanding attachment elements radially clear ofthe stent holder 24. In the unlikely event that any attachment element68 may remain engaged to the stent holder 24, the ramp surfaces alsoprovide a facility to free the attachment elements by slight axialand/or rotational movement of the delivery catheter, which encouragesthe attachment element to ride against a ramp surface.

D8: Following release of the stent-valve 10 from the accommodationregion, a first step of removal of the delivery catheter may be towithdraw the portion of the delivery catheter that is distal of thevalve leaflets 136, through the valve leaflets to the proximal side(e.g. into the ascending aorta). Thereafter the, the delivery cathetermay be withdrawn with the sheaths 20 and 22 open or closed.

It may be appreciated that the

-   E: Removal of delivery catheter while open (after step D):

E1: The delivery catheter may be withdrawn without any furthermanipulation or translation to close the sheaths 20 and 22. If theinterface member 50 has not already been deployed from the second sheath22, the second sheath 22 may be further translated open (proximally) torelease and deploy the interface member 50.

E2: The delivery catheter may be withdrawn by pulling proximally throughthe introducer 19. The liner sleeve 150, if used, may remain in place atthe introducer, as the stem is pulled through, or the liner sleeve 150may manually withdrawn or may self-withdraw as a result of friction.

E3: As the distal portion of the delivery catheter approaches theintroducer, the second sheath 22 may pass smoothly into the introducer,by virtue of the streamlined shape of the third tube coupling 44. Theinterface member 50 may translate distally to abut the stent holder 24,either by virtue of the movement of the catheter in the blood stream, orby contact between the interface member 50 and the end of the introducer19. As explained previously, the interface member 50 has a shape thatpresents a streamlined profile to guide the distal portion, with thestent holder 24, smoothly into the introducer. The distal portion maythus be withdrawn through the introducer even when the sheaths are open.The inter-face member 50 remains deployed during the withdrawal.

-   F: Removal of the delivery catheter with sheaths closed (after step    D, and instead of step E):

F1: If the interface member 50 has not already been deployed from thesecond sheath 22, the second sheath 22 may be further translated open(proximally) to release and deploy the interface member 50.

F2: The first and second sheaths may be translated towards a closedstate, with the first sheath being translated proximally, and the secondsheath being translated distally. As explained previously, the interfacemember 50 has a shape that may provide a bridge or interface between theends of the two sheaths to define a smooth profile without abrupt edges.The distal portion may thus be withdrawn smoothly through theintroducer. The interface member 50 remains deployed during thewithdrawal.

F3: The liner sleeve 150, if used, may remain in place at theintroducer, as the stem is pulled through, or the liner sleeve 150 maymanually withdrawn or may self-withdraw as a result of friction.

It will be appreciated that the foregoing description is merelyillustrative of preferred forms of the invention, and that manymodifications, equivalents and improvements may be used within the scopeof the invention.

The invention claimed is:
 1. A transcatheter aortic valve implantationsystem, comprising: an aortic stent-valve comprising a stent componentand valve leaflets supported by the stent component, the stent componenthaving an inflow end and an outflow end and being self-expandable from acompressed condition for delivery towards an expanded functionalcondition, the stent component comprising outflow structure at theoutflow end, a crown intermediate the inflow and outflow ends, the crownhaving a free extremity intermediate the inflow and outflow ends anddirected towards the outflow end, and the stent-component furthercomprising a fixation section between the crown and the inflow end; adelivery catheter having a distal portion insertable into the anatomy,the distal portion comprising a stent-valve accommodation region foraccommodating the stent-valve in the compressed condition for delivery,a first sheath for covering at least a portion of the fixation sectionat the accommodation region to constrain the fixation sectioncompressed, and a second sheath for covering at least a portion of theoutflow structure and at least a portion of the crown at theaccommodation region to constrain the outflow structure and the crowncompressed, the second sheath being translatable in a proximal directionto uncover the crown and the outflow structure for deployment, and thefirst sheath being translatable in a distal direction to uncover thefixation section for deployment; wherein in a condition in which thestent-valve is loaded at the accommodation region and the system isready for introduction into the anatomy, the first and second sheathsare spaced apart from each other in an axial direction such that aportion of the stent-valve is not covered by either sheath.
 2. Thesystem of claim 1, wherein the outflow structure comprises a pluralityof arches having apexes at the outflow end of the stent component. 3.The system of claim 1, wherein translation of the second sheath deploysthe crown followed by the stabilization arches to permit axial seatingof the crown against native leaflets and generation of axial alignmentforces by the arches contacting the ascending aorta, and translation ofthe first sheath deploys the fixation section to anchor the stent-valve.4. The system of claim 1, wherein the stent-valve is configured suchthat, when the first sheath covers at least a portion of the fixationsection, and the second sheath is translated proximally to uncover thecrown and the outflow structure, the stent component defines a partlydeployed substantially flared shape from the portion of the fixationsection constrained by the first sheath, towards the free extremity ofthe crown, the flared shape permitting universal seating of the crownagainst native leaflets.
 5. The system of claim 4, wherein the partlydeployed substantially flared shape corresponds to the crown beingpartly deployed in a form smaller than its fully deployed shape.
 6. Thesystem of claim 1, wherein the stent-valve further comprises an innerskirt covering a portion of an inner surface of the stent component, andan outer skirt covering a portion of an exterior surface of the stentcomponent, the inner skirts including a region of partial overlap, andwherein the space between the first and second spaced apart sheaths isin register with at least a portion of the region of partial overlap ofthe inner and outer skirts.
 7. The system of claim 1, configured fortransvascular delivery of the stent-valve to the heart.
 8. The system ofclaim 1, wherein the first sheath is shorter than the second sheath. 9.The system of claim 1, wherein the first sheath and the second sheathare non-overlapping and/or have a same diameter as each other.
 10. Thesystem of claim 1, wherein the delivery catheter further comprises aninterface member at the accommodation region, the interface member beingdeployable upon translation of at least one of the sheaths, theinterface member providing a guide surface for aiding withdrawal of thedelivery catheter from the anatomy after the stent valve is deployed.11. The system of claim 1, wherein the delivery catheter comprises aflexible stem portion extending between the distal portion and a controlhandle at a proximal portion of the delivery catheter, the stem portioncomprising a plurality of flexible slidable tubes nested one withinanother for controlling translation of the sheaths in response tooperation of the control handle, wherein the control handle comprises anactuator for applying pre-tension to at least one of the tubes forbiasing the first sheath in a proximal direction.